I have not noticed my OBi202 rebooting on its own. Current uptime is 27 days.
It does not use OBiTALK Provisioning or Service. It and my LAN are on UPSs. The ISP is solid cable via a solid modem, router, and switch.
An easy first step would be to disable the OBiTALK Service... proprietary stuff is less useful than standards-based stuff, imo. And their cloud services seem to fall down every week. So, turn them OFF and see if your OBi is more stable. It should not be rebooting... not reliable networking behavior.
Also, somewhere in the Admin Guide they claim poor configuration settings can cause rebooting, but I would expect this to happen more immediately, not after days of uptime. (Or maybe during specific use such as of the dial plan settings.)
Also, a marginal power supply could affect circuit stability. You should have a backup OBi202 on the shelf, right?, so you could trial its AC adapter... or the whole thing.
OE