Quote Originally Posted by Photo Engineer View Post
If the scanner brings out abnormalities, then the problem is in the film. Does that make sense to anyone?

No. The negative can be flawless, but if the bulb or sensor have even the slightest abnormality, it will affect the scan, just like a scratch on the condenser bottom glass.

Once again OP - can you see this issue on the negative with your own eyes?

What scanner are you using?
Is the scan you uploaded earlier modified in any way?

Try scanning any other underexposed negative you have which has previously seemed to be OK to you, and see what you get.