I’m sorry you went through that pain. Timeshift isn’t an app we use for fun. Timeshift is meant to save the ass; not make things worse. Technically, if you restore a snapshot, reboot (edit your boot selection), log-in and finally update-grub, it’s perfect and as it should be.
But, if you don’t know this, it’s possibly the worse experience you’ll ever have on Manjaro. Hopefully it’s a bug and will be fixed. So, until then, just finish it manually and you’re good to go <3