After adding more RAM to guest system and restarting it gives “Error 16: Inconsistent filesystem structure” like in the first screenshot. I tried all four options in the second screenshot, but unfortunately the guest system still doesn’t want to come up.
Googling didn’t give any results for the subject on www.virtualmin.com, but other sources suggest to start with initial grub. I don’t know how to do it. I hope it is possible to do that from host system.