This is the assembly instruction that’s generating the exception:
const FQuat newQuat = inputQuat * rotQuat;
00007FF84FF81A15 movaps xmm3,xmmword ptr [rbx]
From what I can tell, the issue is the use of movaps here, which expects aligned operands.
Byte patching/hex editing this instruction to movups (the unaligned variant) fixes the issue, which would seem to indicate an alignment problem, but using __declspec(align) to try to force the alignment doesn’t seem to help. Perhaps one of Epic’s engineers can investigate further on this basis.