Control points randomly non-selectable in the Local Adjustment menu.

I’m on an iMac 27", 24gigs of ram, Mojave 10.14.6.
After working for a while the Control Point option in the Local Adjustment menu stops functioning. The only way I’ve found to make the control point selectable again is to restart PhotoLab. I can then continue to use the control points until it becomes non-selectable once again at which point I have to repeat the above solution.