Over the last few months, and several versions of BOINC the manager has been crashing with the "RPC password corrupt" error message. BUT this only happens when the manager is neither minimised to the task bar, or active as a visible window.

The following do not affect the problem :-
Running Virtual Box (LHC);
WGC (various sub projects);
Denis;
SiDock;
Universe;
Einstein
Any combination of the above, with up to three different projects selected, visible or minimised BOINC runs all day without problems, sitting in the notification area BONC manager will crash after a variable length of time (minutes to several hours).
Checking using windows task manager shows that BOINC and the tasks are still running, but cannot be controlled.
The PC is a Ryzen 7 3700X (virtualisation active) with 32GB RAM, running Windows 10 Pro.
BOINC is currently version 7.20.2, but this behaviour has been consistent over a number of older versions.

I have two work arounds:
If I remember I open BOINC manager and minimise it to the task bar;
or if I forget and the manager has crashed I exit BOINC (maximise, right click, exit).

Does that equate to my unresolved bug report https://github.com/BOINC/boinc/issues/4460?

I have had the same exact error on just about all my Windows PC running BOINC. If I recall, it started occurring sometime after upgrade to the 7.16.x versions.

BOINC open and running in a full or minimized window or even in background in the system tray with icon showing.

Like Richard indicated it might be a CPU BOUND or possibly even a MEMORY BOUND issue as described in the GitHub ticket.

Yes and no.....
Error message is the same.
BUT
This even happens when the CPU is far from bound (I'm using max half the cores), and it happens when there's noting else (known) to be running.
It even happens with only one task in progress, and so very low CPU loading.