FMC920 on move updating not following settings

I have an FMC920 in a vehicle that was set to update “on move” every 5 seconds, which it did, for months, and set to every 2 minutes on stop. Credit ran out on the EE sim card and upon payment it started to work again, but a few days later there were a series of long outages from the local cell tower, which is notoriously unreliable and is constantly playing up.

I can’t say if my issue was caused by the SIM card running out of credit, the cell tower issues, or an issue with the FMC920 itself, but since these occurrence I noticed it updated on the move only every twenty seconds. I can set it via SMS to update both on the move or stationary to LONGER than 20 seconds and it obeys. Anything less and it stays at 20 seconds.

My settings for “On Move” below, any advice welcome, thanks for reading.

Via SMS getparam shows:

10050 Min Period 5
10051 Min Distance 15
10052 Min Angle 10
10053 Min Speed Delta 10
10054 Min Saved Data 1
10055 Send Period 5