Looks like some issues spawned. After the update in the same scene as in 2.3.6, at first mouse got impossibly sensitive and game started to lag intensively / jitter on more CPU intensive angles. Before 2.4.1 it was around the same framerate (with the exception of sniper rifle as shown) but the view didn't lag the controller.
Now it behaves like this:
Note how the weapon jitters. Also, sniper rifle seems extremely unusable, could probably benefit from some optimization.
Before updating, Opsive/Shared and Opsive/UltimateCharacterController were removed as instructed, then Installation performed.
Oversensitive mouse was fixed by rebuilding the character through Character Manager. Although it still might be a little faster than in 2.3.6.
The issue is present on every character previously working normally. Might not be noticeable in demo scene as it's very light cpu/gpu-wise, but I say it's there too. Movement slows down when something more complex is in the view.
Oh, one more thing:
In 2.3.6 on the same scene the movement and rotation of the UFPS was very jittery when in FixedUpdate mode. The only way to fix it I found was to set Update instead. Now it's that way too, but Update is a little jittery as well.