My thinking was that a process is hanging on the default timeout.
The test above may have helped figure that out, but I am still uncertain as you point out that you closed the terminal with the message that a process was still running.
Maybe we can try to backtrace the hanging worker:
Also, you may try booting from an Earlier Kernel, as you say:
This implies an update to the system (Which recent updates brought newer kernels) may be the cause.
From Grub, tap tab ot left shift or esc to bring up Advanced Options for Zorin and then choose an earlier kernel.
If earlier kernel works, please see here: