Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2070 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 452.06
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-08-25 19:28, hash: rB396d39c6b904
Worked: never before has this ever worked correctly.
Short description of error
When box selecting multiple bones in edit mode and they occlude each other making impossible to select all of the ones you need only allowing you to switch to other selection modes like circle select or lasso select.
Exact steps for others to reproduce the error
Open a character with multiple bones mounted onto each other.
go into edit mode
try to select a large group of bones via box select
result: some get selected some not, no matter how many times or different angles you try.
note: Lasso picks up all of them afaict
note: this also seems to work better in posemode
Here is a gif depicting the issue.