tldr; this bug is still here and annoying aF. I've returned to using Version 10.7.6
Config: 2 monitors in use with MacOS 10.14.6 "Mojave" (yes, i know!).
The App Store stopped working for me last year, so i got stuck on RDP version 10.7.6. Recently we got Yubikeys at work, which were not yet hot-pluggable in that RDP version. Collegue using the same setup, but with current RDP version, told me that they did not need to reconnect a session after plugging in a yubikey.
So I decided to finally debug and fix that Store problem, not knowing about other ways to obtain a current version. Massive pita, but eventually got it. Upgraded to RDP 10.8.1 and got this bug driving me mad during the next week working from home, until i realized that it's a client-side problem when i returned to the office and the problem was nonexistant at the physical machine.