Exchange error popup every 5 seconds

I logged in to the Exchange Admin Centre today and I started to see frequent Exchange error popup every 5 seconds or so. The message I get all the time is this: “Error. Your request couldn’t be completed. Please try again in a few minutes.” Everything else works fine. How do I stop this and what would be the root of the problem?

Hey Rex,
Due to reported bugs on Exchange 2019, I suggest you to try this:

Use “https://<Exchange 2019 Server>/ecp/?ExchClientVer=15.2” to access Exchange 2019 ECP.

Move all mailboxes to Exchange 2019 and decommission Exchange 2013. When we shutdown Exchange 2013 services this behaviour change and no issue occur.