FEX 511G 5G keeps flapping 5G

Hi, we are attempting to use private 5G with a FEX 511 5G however the device is consistently flapping. It looks like the logs state that the modem is rebooting every 5 mins or so. On the P5G side we just see disconnects and reconnects. We have 2 FEX 511Gs (one outdoor and 1 indoor) with different modem hardware and are still getting the same issue. We also have a FG-50G-5G presenting no issues with the connection and every other device such as mobiles are not presenting an issue.

The issue seems to be localised to the device. Is this a known issue/bug or has anyone else experienced anything similar and if they have, how was it solved?