Thank you, looking there was pretty revealing.

Under "template": I had the correct file but the path was for HPC, not for my local computer, on which I ran the analysis.

Normally my scripts are safe against running part of the analysis in one context and another part in the other, but earlier today I was experimenting with something and apparently somehow got these folders crossed.

I mean, I still have no idea how EXACTLY it could have happened, i.e. where afni_proc got this HPC path from. I see no plausible source, and, interestingly, if I search for a part of that HPC path in afni_proc.py's output or proc, it's not there. But some other things were messed up from trying small bits at a time and this must have been a side effect.

l'll re-run it properly and I hope everything will be fine.