I have the same problem, but didn't use Flashify. For me the random hangs are followed by a reboot too, but happen very rarely (once every few days) so I didn't try to fix it yet. Just yesterday it hanged twice in a row, after which it was fine again. Would it help to send you some kind of log @flar2?
*edit: Stock H2OS (magisk 13.3) +EX 1.06 (stock settings)
Yes, you need to send the contents of /sys/fs/pstore/
If you are overclocking, stop. I can't think of any other reason for instability. I have not had any reboots.