As far I understand, with the 400 fortepan you have problems with bright points in the film, in other films not problems.
Sounds like a manufacturing defect of the film.
I had similar problems with negative EASTMAN PLUS-X - 5231 (discontinued manufacture over a year ago).
In my negative I have black spots. I pulled a few feet of film to light and with magnifying glass I saw these defects in the emulsion. I have seen and bright points in the emulsion. Defects were more rare than you.
George