F5-422 joined to domain. Issues updating domain's users and groups

[htxwmc]

TNAS model: F5-422
TOS: 4.2.28-2201191742

We were able to join the TNAS to our domain. But, it does not seem to be loading the domain's users and groups. It takes a while and in some cases we get the message:

400 Bad Request
The plain HTTP request was sent to HTTPS port
nginx/1.18.0

Any help is really appreciated.

[TMSupport]

Not clear what the reason is, please contact our tech team to have a remote session.