Thanks for the log and configuration information. After working through it and WeeWX, I believe that everything is working as designed.
From the log, I will assume your archive_interval is 300 and archive_delay is 15.
During this time of the log, MQTTSubscribe is chugging along, but nothing has been received and therefore the loop packet is ‘passed through’.
Feb 6 15:44:53 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:44:53 CET (1612622693): dateTime: 1612622693, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 59, windSpeed: 9.0
Feb 6 15:44:56 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:44:56 CET (1612622696): dateTime: 1612622696, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 53, windSpeed: 11.0
Feb 6 15:44:58 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:44:58 CET (1612622698): dateTime: 1612622698, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 65, windSpeed: 12.0
We have now passed the end of archive interval (5 minutes). WeeWX ‘puts aside’ the accumulated loop data for this interval (15:40 to 15:45) and starts accumulating data for the 15:45 to 15:50 archive interval.
Feb 6 15:45:01 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:01 CET (1612622701): dateTime: 1612622701, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 63, windSpeed: 12.0
Feb 6 15:45:03 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:03 CET (1612622703): dateTime: 1612622703, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 61, windSpeed: 12.0
Feb 6 15:45:04 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:03 CET (1612622703): altimeter: 29.905, dateTime: 1612622703, dewpoint: 29.2, heatindex: 31.1, inDewpoint: 45.5, inHumidity: 42.4, inTemp: 69.3, outHumidity: 92.4, outTemp: 31.1, pressure: 29.306, radiation: 7, rain: 0.0, rainRate: 0.0, signal1: 0, txBatteryStatus: 0, usUnits: 1, UV: 0.0, windchill: 22.7, windDir: 61, windDir10: 69, windGust: 16.0, windGustDir: 44, windSpeed: 12.0, windSpeed10: 9.87
Feb 6 15:45:06 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:06 CET (1612622706): dateTime: 1612622706, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 74, windSpeed: 12.0
Feb 6 15:45:08 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:08 CET (1612622708): dateTime: 1612622708, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 74, windSpeed: 12.0
Feb 6 15:45:11 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:11 CET (1612622711): dateTime: 1612622711, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 64, windSpeed: 12.0
Incoming MQTT data is received and queued up.
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) MessageCallbackProvider data-> incoming topic: pegel/566055/Q, QOS: 0, retain: 0, payload: b'41.3'
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> incoming pegel/566055/Q: Q566055v: 41.3
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) MessageCallbackProvider data-> incoming topic: pegel/566055/W_cm, QOS: 0, retain: 0, payload: b'156.0'
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> incoming pegel/566055/W_cm: W566055v: 156.0
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) MessageCallbackProvider data-> incoming topic: pegel/567470/Q, QOS: 0, retain: 0, payload: b'87.4'
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> incoming pegel/567470/Q: Q567470v: 87.4
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) MessageCallbackProvider data-> incoming topic: pegel/567470/W_cm, QOS: 0, retain: 0, payload: b'153.0'
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> incoming pegel/567470/W_cm: W567470v: 153.0
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing pegel/566055/W_cm: dateTime: 1612622713.6558828, usUnits: 16, W566055v: 156.0
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing accumulated pegel/566055/W_cm: dateTime: 1612622713, usUnits: 1, W566055v: 5.118110236220472
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing pegel/566055/Q: dateTime: 1612622713.6551414, Q566055v: 41.3, usUnits: 16
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing accumulated pegel/566055/Q: dateTime: 1612622713, Q566055v: 1458.49711, usUnits: 1
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing pegel/567470/W_cm: dateTime: 1612622713.6563249, usUnits: 16, W567470v: 153.0
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing accumulated pegel/567470/W_cm: dateTime: 1612622713, usUnits: 1, W567470v: 5.019685039370079
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing pegel/567470/Q: dateTime: 1612622713.6561482, Q567470v: 87.4, usUnits: 16
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) TopicManager data-> outgoing accumulated pegel/567470/Q: dateTime: 1612622713, Q567470v: 3086.50478, usUnits: 1
Loop packet is updated with MQTT data and will be accumulated by WeeWX with other loop packet for the 15:45 to 15:50 interval.
Feb 6 15:45:13 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:13 CET (1612622713): dateTime: 1612622713, Q566055v: 1458.49711, Q567470v: 3086.50478, rain: 0.0, rainRate: 0.0, usUnits: 1, W566055v: 5.118110236220472, W567470v: 5.019685039370079, windDir: 71, windSpeed: 9.0
Feb 6 15:45:16 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final packet is 2021-02-06 15:45:16 CET (1612622716): dateTime: 1612622716, rain: 0.0, rainRate: 0.0, usUnits: 1, windDir: 73, windSpeed: 10.0
The archive_delay has passed so WeeWX creates the archive record for the interval from 15:40 to 15:45. Since no MQTT data was received between 15:40 an 15:45 it is retrieved from the cache.
Feb 6 15:45:16 LokalWiki weewx[153466] DEBUG user.MQTTSubscribe: (Service) data-> final record is 2021-02-06 15:45:00 CET (1612622700): altimeter: 29.905125, appTemp: 21.328939698162554, barometer: 29.940951730031646, beaufort: 3.0833333333333335, cloudbase: 1011.3178296862307, dateTime: 1612622700, dewpoint: 29.15000000000001, heatindex: 31.141666666666676, humidex: 31.141666666666676, inDewpoint: 45.56666666666667, inHumidity: 42.38333333333332, inTemp: 69.38333333333333, interval: 5.0, maxSolarRad: 79.66887450173137, outHumidity: 92.25, outTemp: 31.141666666666676, pressure: 29.30612499999999, Q566055v: 1522.06357, Q567470v: 3128.88242, radiation: 11.041666666666666, rain: 0.0, rainRate: 0.0, signal1: 0.0, txBatteryStatus: 0.0, usUnits: 1, UV: 0.0, W566055v: 5.216535433070866, W567470v: 5.05249343832021, windchill: 22.825000000000003, windDir: 65.28102854956737, windDir10: 69.79166666666667, windGust: 21.0, windGustDir: 70, windSpeed: 10.73611111111111, windSpeed10: 9.68
And the processing continues.