As Nick says, the antenna activity on those timeline really does vary, and gaps aren’t unusual. And yes, it can also be due to bad connections or faulty antennas.
Something does look a bit odd with those though. The GPS bar is unbroken, so something is being transmitted over the cell network. All 4 FCD turn off right at the time the “reboot odomter” increments. Following that, several FCD do come back online, often at the same time, before cutting out again often at the same time.
This may be related to a very long-standing issue related to how multiple FunCubes are handled by some versions of SensorStations and Raspberry Pi-based SensorGnomes. The issue has been fixed by CTT in later versions of the SS software image, though there remains an inherent challenge in running more than 3 FCD while also running the cell modem and WifI module. The newer SS software provides toggles to turn the cell and / wifi off if needed. You can read more about that at the link below. Hopefully the steps here resolve your issue!