Mystery Oil Dump 87 Golf

I have an 87 Golf, gas, and I started getting an oil pressure light when I rapidly decelerated after long periods at high speeds. I looked it up, changed the switches, then dropped the pan. a note: have not done that before Based on my limited experience, the intake screen looked pristine, hard to find anything that could be called gunk anywhere around. Put the pan back on with a gasket and silicone, filled back up with a heavier oil, and ran it for a while on the blocks, then to the store around the corner with no leaks in sight (seemed, from the way it sounded, much happier with the heavy oil). So then I started to drive it to work, 5.5 miles away. All great until mile 4.5, when the low-rpm pressure light went off (for the first time) and I pulled over to find basically NO oil in the system.
Had it towed back across town and asked my mechanic to redo the pan installation since obviously not worth the destruction of the engine (if it had anything left, poor car) to develop my mechanic skills. But then he said the pan installation is fine, it’s not leaking, didn’t look like any silicone had slipped in, and the leak was in the pcv system. He showed me all the sheen over there. But I should emphasize that I would call it more like a dump than a leak: 100 to zero in a mile or two. Also, I do not remember smoke, though maybe I just didn’t notice.
So since then he has been trying to figure it out and no luck. He checked the compression and it was 150 all the way across. One thing I had worried about, what the manual is calling the oil intake baffle, which is different than baffles on a lot of cars, I had broken a couple of the 4 clips than hold it on to the intake and thought it might not hold, but he said it was still attached in place when he was there. He’s a fabulous, trustworthy guy but usually works on american cars so he also asked 2 people he knows who work on VWs and everyone is out of ideas.
Do you have any thoughts about what to investigate? I feel that it MUST be somehow related to what I did with the pan. Thank you so much!
-m