I have some good news for you: our Rocky8 VMs have been updated to 4.18.0-553.134.1.el8_10.x86_64 (and some even to the latest 4.18.0-553.141.1.el8_10.x86_64) kernel on 24th June (3 weeks ago). Since then the problem disappeared completely and today we continued our V2V migration from VMware to XCP-ng. Thanks for all your support!