Problem regarding character's mesh while playing montage

Hello fellas, currently i am dealing with a problem regarding my character’s mesh while it plays a montage (see video for reference).

The left mannequin is the simple animation dragged into the scene, that’s how it should look.

The right mannequin is my character, playing the same animations as a montage and triggered through the character’s BP (pressing space/jump). As you can see, the mesh gets deformed for some reason.

Now my question is: Why does the mesh of the character get deformed while playing the montage?

My theorie is that the AnimationBP of the character does interferes with the montage, which is why i post my question/problem here in “Developement > Programming & Scripting > Blueprint”. But i do not know what i am doing wrong exactly…

If needed, i would add some further images of some BP Code-Snippets and settings of the animatiosn. But the code is realy simple and regarding the animations, there is nothing special i did as far as i know (this project is relatively old).

In the character’s BP i just trigger the montage. In the AnimBP, i created a graph-logic for the locomotion, air and on the ledge animations. Maybe i did just set up something wrongly or did miss some other things to change. Does someone has any clue where to begin with?

Here is the video:

Here a overview of the Anim-Graph of the character’s AnimationBP: