@fredrik has mentioned fake ICs a few times and my stash of TL074’s turns out to definitely be. The first sign should have been when I found a single LM324 mixed in, but I didn’t put it together at the time.
I built a PM Foundation State Machine and it wasn’t working. The gate just stayed high.
I’m usually hesitant to contact support for anything, but after a lot of troubleshooting with no luck, I contacted the manufacturer and I got expert help testing and calibrating everything. One of the very first things he asked was if I was using genuine TL074s. The charging circuit is picky.
In any case, the module is now behaving nicely and it’s calibrated better than it would have been without the help. Ergonomics are obviously terrible, but it’s a very powerful module so I’ll just live with that.
Now, off to Anchor for a stash of genuine opamps!