Some of my devices send no data, but are online

Hi, I have a problem with some, but not all of my devices, it didn't happen before until like a week ago. Maybe more, but I haven't noticed.

I have a variety of different trackers - some battery powered, some by OBD2, some by other car connectors. 2G or 3G. Many are made by different manufacturers.
The problem I am having is that some of them (not all) don't seem to send any sort of data to the server, like battery state, alarm etc. - the information panel is literally empty. Nothing is in there, at all. But the device is online, so there's definitely some sort of connection being made.

I have reasons to believe that it's something related to my location - when I received a new sample device I specifically asked the factories technician to see if it works on their platform. It did, but when it came to the company it stopped sending any data to our Traccar server or their own tracking platform. Even they don't have any idea why it won't work, but suggested to turn off Wi-Fi, though that's impossible to do even for a moment. Besides, it didn't cause any trouble a month ago.

Some are just sending wrong location, but I blame it on bad weather for now.

What could be the cause of this problem? Like I said, these devices are wildly different, so it's probably an issue with my location. Is something capable of causing such interference? In extreme case it could be the police officers that often patrol near my company, they could have GPS blockers of some sort, but they're not there 24 hours a day...