Nextcloud very slow in opening webpages in Admin login mode but ok in Standard user

Hi all, I was looking for help with a really strange problem.
I have a nextcloud server with very high hardware resources installed on ubuntu 20.04 LTS.
2 days ago it suddenly became very slow to open web interface pages if logged in with Admin user. The pages take over 8 minutes to load and often go into timeout, to the point that it is impossible to administer the system and users.
On the other hand, if you log in with User Standard users, the pages open normally and uploading and downloading files has no problems. I specify that all logins are done by sending OTP code for two factor authentication.
Does anyone have any idea what it could be and how to solve the problem ?

Since this morning exactly the same problem.
Anybody familiar with this problem?

Nextcloud servers:

are down. This is going into third day. I have no clue if the problem is with the servers themselves or their network.

More info here:

Also, try disabling the updatenotification via command line:

occ app:disable updatenotification

To enable it again, do

occ app:enable updatenotification

@Cook, Thanks a lot!
I just switched off the app, that did it!