I've noticed that sometimes when I use active pause and then un-pause, the plane I'm flying will suddenly become uncontrollable, veering, climbing or descending, and the autopilot shuts off or stays on but isn't working. This happens with different planes. Has anyone else experienced this, and is there a fix for it? There are some things I really like about 2020, but it seems that MS also broke some very simple stuff. Can't save and restore flights anymore, can't even pause without sometimes breaking everything. 

For how long do / did you pause? See that also in 2020 after a longer pause when weather and especially winds changed remarkably in the meantime and the Aircraft seems surprised and needs to cope with the changed situation 

Usually not more than a few minutes, maybe 5-10 minutes tops.