Film Developing (Shooting?) Fiasco

My 5 rolls of Pan F Plus , for the first time, came out virtually way underexposed - little if any density - many frames clear! Is it my camera - shutter malfunction or something? PanF+ has been my main film 4 years now, never a problem, shooting/developing. D76 one to-one as usual.
I'm just saddened & shocked for they were of a project that can't be shot again.

start by looking at the markings on the film edges. If they are faint or non-existent, most likely a developer issue. If the are good, then probably an under exposure issue.

Nige said:

start by looking at the markings on the film edges. If they are faint or non-existent, most likely a developer issue. If the are good, then probably an under exposure issue.

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This would be good advice for any other film except Pan F. This film has a definite problem with fading of the latent image. This means that the edge markings fade from the time of manufacture. So for Pan F this is not a reliable test.

Gerald C Koch said:

This would be good advice for any other film except Pan F. This film has a definite problem with fading of the latent image. This means that the edge markings fade from the time of manufacture. So for Pan F this is not a reliable test.

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Unless of course they are perfectly well defined in this case (i.e. not faded) which would indicate under expsoure.

How much time elapsed between the exposure of the film and processing?

+1 on time between exposure and development. 9-10 months after exposure led to thin negs