Welcome to the Serif Affinity forums.
My first suggestion would be that you open your Photo Preferences (Edit > Preferences), click on Performance, and see if you have the new Hardware Acceleration (OpenCL) function enabled. There's a setting at the bottom of the Performance section. If it is enabled, disable it, close Preferences, restart Photo, and see if that resolves the problem.
A number of users are having problems with that new performance option due to issues with their graphics drivers, so when odd things happen in 1.9 on Windows that's a good place to start.
