BandQ EoY Resprucing: Fix Detached BX lines

Fix incorrect mass windows used for BandQ detached B + X sprucing lines. Please merge this before full-scale end of year resprucing.

Tested locally, works correctly. There was a small bug, but BW should not change too much. Shifter @cacochat still please submit a CI-test for sanity check.

FYI: @hoslee, @ziyiw, @jadevrie, @ipolyako, @shunan, @abertoli