Hi there AndreRebel,
We are experiencing similar issues during testing on our staging evironment.
Click image for screen recording:
Versions we ran:
With all plugins disabled and using a storefront theme (but with a rather large product database of aprox 30k products).
And older versions of wordpress, because we noticed that the demo environment of ATUM runs on these settings (except for atum version maybe?):
What can we do to try to resolve this issue? ATUM looks very promising, so we are hoping to get this fixed soon!