PgAdmin 4.15 stops responding

Hello,

I try to use pgAdmin 4 on Windows 10 with PostgreSQL 12.1, but it is
quite unusable.The application starts, I enter the master password, I
can connect to the server and open the entry for one of my databases in
the tree on the left side of the pgAdmin window. So far everything looks
normal. Then I try to do something with that database - look at a table
definition, look at data, start a backup. Now the cursor usually changes
to a rotating circle, or I click a button and nothing happens. And this
state lasts, sometimes for hours, till I close the pgAdmin window.
Sometimes I can do one or two actions with the database before
everything hangs - but most of the time even that is impossible. This
state of affairs is new, possibly since the update to Version 12 of
PostgreSQL. Before, I usually could do more and pgAdmin stopped
responding later.

My browser is Firefox, but I just tried with Edge - same thing.

I'm using the EDB installer and the pgAdmin version contained in that
package (4.15 at the moment, I think). The PostgreSQL server and pgAdmin
run on the same machine.

What can I do?

Thank you for help!