A bug of LUT component?

i've seen this or something similar before. i'm fairly certain its fixed in newer versions

try using the ROM block instead of the LUT. i don't think it had that problem

i think the problem has to do with the output register of the LUT. try disabling it and using an external delay if the ROM doesn't work

for future reference i think a couple of other blocks had problems with the output register so if your hardware doesn't match Simulink either update to recent software or take a look at post-fit netlists to see if you can see the register disappearing