Pro 12 freezing when using 'Whiteout'

[Evan]

Using Pro 12.2.0.228 on a 2007 iMac that is partitioned with Win 10, 32-bit, x64-based processor. 6 GB ram (says 2.98 usable). I have been heavily using the 'Whiteout' feature to clean some PDFs recently. I can only safely conduct about six whiteout events at a time before I have to manually Save, because at any time during this PDF manipulation, the program will freeze and the page goes white (and sometimes partly black). I have to close (click 'No' to the Save prompt) and relaunch the program. This does not happen on our Pro 11 365 program at my government department. What is causing this instability?

PS: I would include a screen print if I knew how.

Evan