Several sources for pinholes:(posted 8918 days ago)1. Airbubbles form on the surface of the film when the developer is poured in. If this is the problem you can do a presoak with water before you put the developer in. This may require a slight increase in your development time. Or you can give the tank a few raps on the countertop after the developer is in so dislodge the bubbles. I do both.
2. Using an acid stop bath can cause developer dissolved in the emulsion to emit a gas, taking some of the emulsion with it. A weaker bath or just a water bath will solve the problem. I recommend water.
3. I actually had a few rolls of film in the 80's where it appeared that there was a manufacturing defect in the film.
That's about all I know on the subject.