Microsoft Remote Desktop wont stay full screen on MacBook Air

My wife has just upgraded a very old MacBook to the latest MacBook Air (2020 M1). She uses Microsoft Remote Desktop to access her work computer remotely but whilst it launches fine, whenever she swipes across to the MRD desktop it instantly flicks back to her main desktop. Running MRD in ‘windowed’ mode works fine, but the space taken by both the Mac and windows dock is a problem and makes the screen too small. It works fine on our iMac (also OS 12.3).