Hello,
This is a known issue.
RnD is working on a solution at the moment, but it is planned to be included only in 7.4 firmware release.
Otherwise, It is possible and I suggest to revert to a working firmware version for a while, if that does not create any inconveniences to you.
Alternatively, could you login to the device via SSH and test if any of the commands below restarts WiFi interface to a working state:
- /etc/init.d/network restart
- reload_config
- /sbin/wifi reload
If any of them works, it could be included in the startup script in System -> Custom scripts section, to automate the restarts.
Best regards,