I have enjoyed learning the new Masking capabilities for the last 3 weeks or so and have gradually started doing more complex things with them. I have a reasonable powerful desktop HP system but I have noticed it is obviously slow to complete some of the new tasks. Me getting ahead of it may be a factor. Once yesterday afetrnoon and again this morning I experienced a behaviour where an edit step did not properly end when I thought I had, and it started looping trying to use more and more memory on each loop. Interestingly, while no keystroke could end it, it did sometimes interpret cursor moevement as further input to a mask edit. After each loop it logged something about Camera Raw in the edit history. I had to 'end task' to stop it, then reboooted to be sure it was cleared. It has not recurred yet after sevral more image edits today. Images are all RAW from my D850.
Another problem with a mask edit today. This one did not become a tight loop inside the mask edit but the PC got very slow and did not recover when I exited Lightroom. I had to reboot to clear it. I retried and was able to complete the same edit with out the slow down recurring.