Strange behaviour when BP Editor NOT open


I recently started to work with Unreal as part of my studies and taught myself everything I know so far through online resources. For my current project, I downloaded the UE4Duino Plugin to hook up my Arduino Uno to read the input of a few analog elements like sliders and so on. After I managed to get everything working and streamlined the code as far as I could, my Interface was behaving quiet nice, except one little strange behavior.

When I start playing the scene and the Blueprint Editor is open and visible, everything is read in realtime and the input is nice and snappy. As soon as I close the Editor and hit play again, my inputs are still kind of working except a few glitches.

There is a slider for opacity, a knob that selects a texture and a button the loads the texture into a material.

So when the editor is closed, the button to load the texture gets practically ignored and the opacity is glitching around.
I couldn’t really make sense out of it since I also implemented gates that would ignore overwrites if the new input is the same as the old one and so on.
The glitch also persists if I open the editor after I hit play, I have to open it first and then restart the scene to get the desired behavior.

So I’m wondering if that is somewhat of a known glitch or something that somebody else experienced before?