After trying to downgrade manually, Virtualbox complains that some kernel modules have a wrong version and I cannot fix it. I tried to downgrade my Virtualbox back to 5.1.34, but apt-cache showpkg virtualbox says that the only version available for my system is 5.2.10.

The log is from Android 6.0 (64bit) that booted normally (no snapshot). virtualBox install android-x86-9.0-rc1 stuck in detecting android-x86 found at / dev / sda1 problem solving, Programmer Sought, the best programmer. I tried to read the log of a VM that crashed, but I don't really understand what to look for. This happens to my old VMs as well as some new VMs I tried to make. Whenever I want to run an Android x86 VM (I don't have any other systems), it boots (or loads when I run it from a restored snapshot) fine but after a few seconds it crashes (the window closes and the state of the VM in the menu is Aborted). Now I performed an update of my distro from 17 to 18.04 and together with that, Virtualbox updated to 5.2.10. Until recently, I had Virtualbox 5.1.34 and Ubuntu (Mate) 17 and everything worked fine. For testing purposes I often use Android x86 VMs in Virtualbox (I know they're not officially supported, but they work fine).

Virtualbox android x86 5.1