3 second freezes in custom EditorWindow using UIElements

I'm trying out the new UIElements/UI Toolkit for making editor tools. I started on a simple behaviour tree editor and wanted to see how the new UI system performs with a bigger amount of nodes. Creating around 40 nodes with some basic VisualElement containers, Labels and Buttons I noticed that after every 10-20 seconds of interaction the editor would freeze up. The EditorWindow itself is still very responsive otherwise and I'm not sure what is triggering these big freezes. Here is a video of me just moving around the main container (working smooth) and then after a while it freezes and sometimes even gives a "Hold On" loading popup.

This is what a deep profile looks like:


Anyone else having this issue? What are your experiences with stress testing the new UI framework for editor tools? Is there something I can do to prevent this from happening?

EDIT: forgot to mention I'm using the 2020.1.0 beta, I have this issue on b5 and b12.

 

Weirdly enough I'm not experiencing these lag spikes anymore. I didn't touch the project for a couple of days and it all seems to be working smoothly now. No idea why... I'll submit a case if I get it again.