What accuracy are you using?
High Accuracy
You can read this to understand how things work:
https://www.traccar.org/client-configuration
https://github.com/transistorsoft/flutter_background_geolocation/wiki/Philosophy-of-Operation
You can also try the highest accuracy. That might be more consistent, but using more battery.
Monitoring a number of devices on my server today I found that the update rate from the clients was not as often as I was expecting. Clients are on motorbikes and when moving they were updating about every 5 minutes but are set to the default 75m distance and fastest interval 30s.
So I was expecting an update every 75m or 30s (if moving at more then 9kph).
Is the algorithm for determining expected update rate available?
Clients are version 9.6.4 and server is 6.6