Notes

When trying to move virtual machines away from one of our ESXi servers, the vMotion process fails at 21% with error 195887371.

I discovered lots of sites (like this and this) describing to check the network settings and service bindings. But the settings were all correct.

In the end, we had to move away the virtual machines manually by first powering them off and then we had to reboot the ESXi server. In addition, we also found out that some RAM modules failed and we had to replace them.

I don't exactly know wether the reboot or the RAM replacement did the trick, but I guess, it was the reboot.