Hi,
We have also started to experience this issue at a customer site who RDP to virtual Windows 10 machines (VDI) from their laptops that have remote access software. The issue only started after upgrading from 1909 to 20H2.
Currently the only "work arounds" are to reboot the machine or log in as an Admin via RDP to disconnect the problematic session, neither of which are fixes. Alternative accounts can RDP fine to the machine whilst the primary user experiences the "Please Wait" issue (tested from different machines).
I notice in the event viewer logs there are a lot of disconnect and reconnection messages (Event ID 40 code 0 and 5). Just waiting for further information from the customer as the disconnects do not correlate with what they are telling me is happening.
This is definately an OS issue though and Microsoft need to look at this.