There’s multiple noticeable issues.
I think that, at a base level, the issue is the montage itself.
It needs to transition back all the way to something that at least resembles the idle stance.
From then on, the blend values should be enough to prevent stutters.
And let’s not go into overcomplicated setups.
You could fix it by what we can refer to as “black magic” but it will cost you time.
Just adjusting the animations is usually less than an hour’s work, making complicated setups just overcomplicated junk… if you can make animations…