Onlyoffice connects and disconnects repeatedly

Since about week and half to two weeks ago, files opening with OnlyOffice document server is having connection issues on NC27.

When I open a file like xlsx, I get connection is lost message and connection restored message every few seconds, like the pictures below.

This was working fine like week and half to two weeks or so ago. I’ve update the OnlyOffice App on nextcloud to 9.1.2, so this may be the cause but I’m not sure.

I haven’t changed any configuration so, maybe that could be the issue, if some configuration updates are required, but, I could not find any.

I’ve also created a new nextcloud server with OnlyOffice on NC28, and the result is the same.

Does anyone know what could be the issue?