This is a question (with a potential follow up PR) so someone please tag it accordingly.

Hybrid A* operates with quantizied angles (72 bins by default) so it converts all angles (including start and goal poses) to a bin.
It does that by dividing the angles by angle_bin_size (2pi / 72) and getting the integer part using floor. This introduces quantization errors of up to 0.087266463 radians, which can be a problem in some cases, e.g if the goal yaw tolerance is smaller than that number.

On this PR over our backport of smac_planner to ROS 1, I'm replacing floor with round, halving the worst case error to 0,043633231.
I can open a similar PR to this repo, if the maintainers consider it a positive change.