I'm sorry to hear that you're experiencing issues!
This should definitely not be the case. Only RMS functions like VPN Hubs and router management should stop functioning. This is just an unfortunately-timed coincidence.
Perhaps something else has changed? Maybe the router was moved to a different location? Or different antennas are used?
It could very well be related to your ISP throttling the speeds as well.
To check if there is nothing wrong with the configuration itself, I'll ask you to generate and upload a Troubleshoot file. It can be generated by navigating to System → Administration → Troubleshoot. The file itself can be attached to the original post. It will only be visible to Teltonika moderators.