Here’s Sucuri’s answer to my mail, if anyone’s interested:

Thanks for sending us issues with out SiteCheck site. We know that sometimes it takes quite long it it may look as if the page loading stuck. Sometimes browsers may even show so "connection problems". We are aware about these issues and currently working on a new version of the scanner from-end. We hope it will work much better.

Probably quite few typos :stuck_out_tongue: