1. Run to the right a bit, then to the left. This will cause Sticky Fingers to shoot out his hand and miss. He might do a series of punches instead, which is still fine, but you need to make sure you don't get hit. You MUST move to the right a bit first. If you try to just run to the left immediately and dodge the first attack, you won't get him to be frozen.
2. Run up along the left wall and stop a bit above the section that sticks out a bit. If you go too far, Sticky Fingers will just disappear, which makes re-comboing him harder after the 3rd R2. If you don't go far enough, the glitch won't happen.

https://gyazo.com/bddf9eabeed0234f76e366b3e3095965

3. Use a max-range R2 to hit Chariot Requiem. Do the standard R2-Square combo until Chariot is knocked down. Sticky Fingers should be fixed to one place. You can hit him and he'll block, but he won't ever attack you until he goes back to Chariot. Try to get him towards the beginning of the section so that it takes longer for Sticky Fingers to go back once Chariot gets up.
4. Once Chariot Requiem gets back up, Sticky Fingers will begin to move back towards him. Once he comes out again, the glitch will be reset and he'll attack as normal. R2 him again before this happens and combo him to death (on other difficulties besides Easy, you'll just have to make sure you don't drop the subsequent R2s, since Sticky Fingers will come out faster).

Why does this glitch happen? My theory is that the Sticky Fingers AI gets stuck trying to go back into Chariot Requiem, but can't since you're comboing him. This explains why the glitch resets after Chariot gets up from the ground. Since the AI is stuck trying to retreat into Chariot, it won't do any attacks, even when you hit it. The model gets stuck in one place trying to get back into Chariot. It will still face your direction and block when hit. There may be other setups to get this glitch to work, but this is a fast and consistent way to get it.