Animator Transition lines become thick and overlay the properties pane when swithing OpenGL<->Metal

After switching between OpenGL & Metal, the Transition lines in the Animator controller become thick and overlay the properties pane.

This happens switching to Metal & OpenGL, both ways. To fix this, quit, re-start and re-open project... draw is good (in Metal & OpenGL).

This issue is present since at least 5.6

repro:
(make sure you are in OpenGL to start with)
- create an Animator Controller
- create 3 states with transitions between them
- Edit > Project Settings > Player... ENABLE "Metal Editor Support"...
bug: Transition lines in the Animator are thick and overlay the properties pane
- quit Unity, start Unity and re-open project...
note: you should now be in Metal and Animator Transition lines should look good now.

- Edit > Project Settings > Player... DISABLE "Metal Editor Support"...
bug: Transition lines in the Animator are thick and overlay the properties pane
- quit Unity, start Unity and re-open project...
note: you should now be in OpenGL and Animator Transition lines should look good now.

see attached video of repro (AnimatorDraw.mp4)