I have a script that makes a pgn-graph over the WAN-speed (mobile connection so it varies some over time). I put this image in the Weewx html-root so that Weewx FTP would upload it at the same time as all the other files.
But it doesn't. But only this non-Weewx-file. I "touched" a foo.bar and it got uploaded.
From the #FTP last -file:
pi@RPi-3Bp-Arelien:/var/www/html/weewx $ more \#FTP.last |grep wan
aV/var/www/html/weewx/wanspeed.png
So, what does "aV" stand for? The files that are uploaded get "aS" as a prefix.
I see that some more files as also not uploaded, I guess as they are not changed and hence don't need to be uploaded. But my "wanspeed.png" is changed every 15 min.