A quick update on the MacBook.
I was prompted to submit the issue and looked at the error report details which including this:
Root disk errors: "Could not recover SATA HDD after 5 attempts. Terminating.”
A quick search doesn’t reveal anything too enlightening as, although it would appear to relate to the drive (and maybe APFS) this kind of issue can also occur due to software compatibility issues causing a kernel panic.
More testing required.