It is not your computer's fault. I have never figured out what caused those lines, which have recurred since the beginning. They are on the microfilm itself so there is no way to get rid of them. They will be with us for a couple more days this time, beginning to clear up on the 24th and gone on the 25th and through the end of May. They return in June, but not as severe as we are seeing now.
The lines came from the orginal film canisters as the film was run through the camera it would slide against the plates and catch dirt that would remove film emululsion. This happened with all microfilm I have ever seen of old newspapers. They would have to find and rescan every publication to clean this up.