I'm facing the same issue.
Thanks to your comment I can still get some work done using the content-aware option though, so thank you. Saying that, it does take about 2 seconds for every spot I heal, instead of the previous pretty much instant result.
I should've known better than to update within two months of the release, it's the same kind of thing every time. Luckily I kept the old version as well.
I am having this same issue. I reset all of the preferences using CMD + OPTION (ALT) + SHIFT while starting Photoshop and it fixes it temporarily. However, the problem returns again later.
Edit: The problem has not returned since the latest update to 19.1.1