Forge 1.15.2 recommended version (31.1.0)
Baritone 1.15.2 branch
Cloned after commit e218ced

It happens any time that placable blocks are on the hotbar (dirt to be exact) while the place is at ground+1 level (player Y level). It approaches block placement marker, STOPS (for 0.25 of a second?) and starts to go backwards based off where the camera is pointed to. After going backwards (for 2 blocks?) it tries to go to the same place again. goto STOPS:
It does so until manually pointing camera at the place of interest.

Probably an issue with right mouse button in #mine because #sel fill works fine