VM hangs on Boot after Installation of parallels tools

Hello everybody,
first, I plan to migrate from VMware Fusion to Parallels.
I have two important VMs, both running Ubuntu Server 18.04 LTS. Last thing I did under Fusion was to install latest Ubuntu patches and to remove VMware-tools, then I did a clean shutdown.
Then I fired up Parallels and opened the VMware-VM for import. The import and conversion worked fine, the VM boots normal and I am able to install the parallels tools. After that, I can (without doing a reboot) configure networking and shared folders and everything works fine.
But: Once the parallels tools are installed, I cannot reboot the VM. The boot process hangs forever at some random point. I'am also a bit puzzled why grub isn't showing up when I start the VM, it instantly loads the kernel, I have no chance to enter options or rescue mode.
Any help is appreciated!
Greetings

 

Update: Out of sheer desperation, I tried installing 18.04 from scratch from a freshly downloaded iso yesterday, with the exact same result. Could it be the case that the supplied parallels tools are broken for 18.04? Is it possible to switch to a previous version?