Very frequently alerts will play less than 1x, which was mentioned in a different thread as Camect possibly incorrectly observing upload bandwidth for streaming. This still hasn't been fixed, in my case at least.
Secondly, I will also have some alerts randomly play at 1.1-1.3x speed while actively showing a detected object that is light green (detected status) in the timeline.
Clicking on the speed controls does not always lock in that speed for me either. This could again be due to misunderstanding of available upload speed. My connection is a (very constant) 5 Mb uplink. My cameras are set to 4 Mb streams, so I should be okay for full resolution streaming, but even with the lower resolution default stream, I still will usually not get full speed playback. Realtime video appears to (usually) play frame for frame correctly though.