The initial assumption for your issue would be poor mobile signal quality, specifically:
- RSRP: -113 dBm (values below -100 for the modem used within the router seriously impact quality of data connection);
- SINR: 4 dB (the closer to 0, the more likely the disconnect).
The router itself seems to be able to maintain stable data connectivity. Could you test a different device placement or, if possible, a different antenna?
Also, for testing, you can try updating one of your device's firmware versions. You can find later versions here. Update with Keep settings option set to off. This will clear your current configuration, but will avoid possible migration issues due to significant differences between versions.