Could you check if all of the RUTX11s have the same modem firmware EG06ALAR04A01M4G in Status -> System -> Modem section?
If all of them do, I would like you to install a different version - EG06ALAR02A07M4G in one of the routers with the 7.02.7 firmware.
The instructions are provided here. The ID in your case is 3-1, version - EG06ALAR02A07M4G. See if that changes anything, and, if the issue persists, upload a new troubleshoot file.
Otherwise, if you have a device with 7.02.7 firmware version and EG06ALAR02A07M4G modem firmware, I would need a troubleshoot file from it, as I could consult with the RnD about your issue.