I can reproduce the issue when I use OS3.9 installation + P96 3.2.2 with WinUAE (1920x1080 Zorro 3 gfx board emulation), and Multiview SCREEN <picname> to open these pics: https://1drv.ms/u/s!ApMUGr0cuN39goZj9zBuxX7gqAE5PA?e=7PLsUG
Can't see mouse and RMB to open menu won't work: the screen frame is freezed (I can still quit with the default Multiview key 'Q' though). Winuaeenforcer hits with wild read/writes can also occur.
datatypes.library 44.47 (25-Dic-1999)
picture.datatype 45.17 (19-Mar-2002)
Note: if I boot keeping RMB pressed to skip Picasso96/uaegfx monitor driver initialization thus forcing WB3.9 to boot in simple AGA mode I can't reproduce the issue of course and the pics have no issue when I switch WB window/Multiview own screen.
P.S.
If you can't reproduce it, try first to open pictures in a window with Multiview on Workbench (24/32bit) and then select menu option to move on its own screen.