You should try updating your device, as it might solve your issue, as well as include other features and performance improvements.
Regarding, disconnects, TRB245 has a functionality called Auto reboot, which can be accessed in the WebUI by navigating to Services -> Auto reboot -> Ping/Wget reboot.
Here you can configure automatic modem reboots in case of connectivity loss, without manually restarting the whole device. More details, regarding this functionality and configuration options are provided in this page: https://wiki.teltonika-networks.com/view/TRB245_Auto_Reboot.
If these suggestions do not help you, I would like you to send me a troubleshoot file. Please, replicate the issue, then access router's WebUI, go to System -> Administration > Troubleshoot section and download troubleshoot file from there.