Blender bug report
Operating system: MacOS 10.15.7
Graphics card: AMD Radeon Pro 5700 XT 16 GB
Operating system: Windows 10
Graphics card: Geforce Titan X
Broken: Tried on 2.91, 2.92 & 2.93
Short description of error
Performing point selections in a Grease Pencil object becomes very glitchy when the GP layer is parented via relations to an animated object.
Exact steps for others to reproduce the error
Open the attached .blend file.
Enter edit mode on the grease pencil object.
Attempt to make a box selection. If bug is present, the selection will miss many points.
Scrub the timeline to a new point in the animation. Try make another selection. Notice how hard it is to select points. Tweak mode is also affected.
Here is a screen recording of the issue in case that's useful: https://www.dropbox.com/s/gjtjsfsp7r9tdo1/screen%20recording%202021-02-26%20at%201.27.51%20am.mov?dl=0