Xbox One/Series S/X "Complete Chapter 5 - 2" Achievement Not Unlocking - Workaround

In the Xbox One/Xbox Series S/Xbox Series X version of Resident Evil 5, the achievement for completing mission 5-2 is glitched out and will often not unlock at all. I beat it on Amateur and on Veteran multiple times and it never unlocked. This is how I solved this issue for myself

Here's what I did:

1. I killed the boss Uroboros using the flamethrower (instead of a rocket launcher, pistol or other weapon)
2. Did it on Normal difficulty (instead of Amateur or Veteran which I had done before)

Did the achievement unlock because I finished the boss with the flamethrower? I do not know.
Did it unlock because I did it on normal? I do not know.
Did it unlock because I beat on Amateur AND Normal AND Veteran? I do not know.

Here's what I do know: after beating it on Veteran, Amateur and then Normal, it unlocked. On normal I specifically finished the boss using the flamethrower.

I could not find any information about this bug yet both my friend and I encountered this issue. I had to write down somewhere how I ended up solving it.

I don't know if this same bug occurs on Steam, I just didn't know where else to write this workaround.

Two things to try:

1. Complete chapter 5-2 on Amateur difficulty, killing the boss using the flamethrower
2. Complete chapter 5-2 on Amateur, Normal and Veteran difficilty

Hopefully one of these works for you