This is an IPS patch for Air Buster / Aero Blasters on the Sega Genesis that fixes the freeze in stages 4 and 5.
The bug happens in low gravity sections when you press too many directions at the same time (specifically left, down and right).
The faulty function:
loc_0000D26A:
SUBQ.w #4, $1A(A1)
MOVE.w D1, D2
ANDI.b #$0F, D0
ASL.w #2, D0
JMP loc_0000D27A(PC,D0.l)
; Followed by 11 jump destinations.
At this point, D0's lower nibble contains input information in the form:
direction: RLDU
bit: 3210
There are 11 functions to jump to, so the valid range for D0 before alignment
is (0,10).
A value of 10 corresponds to right (8) + down (2) which is probably the highest you could get using the original hardware. A modern emulator that doesn't filter "wrong" inputs makes it easy to exceed this value and cause a crash.