After vigorous testing each evening, I think I may have discovered what is causing this issue. Below are the list of mods that are green-lit:
However, OpenIV hit an error today and refused to open. I verified my files and it found issues with 14 files. When I got OpenIV working again, it had removed Custom_Maps and MapBuilder from my DLC list.
When I readded them, the weapon animation glitch returned. After several tests of returning them and removing them, the consistent issue is related to Custom_Maps being in my DLC list.
Essentially, if you ae having issues with this animation glitch, try removing Custom_Maps from your DLC list and any YMAPS. Hopefully that solves the issue.