So that's what a computer virus looks like? That, or you're scanning to the cell level, phenomenal resolution.
PSA, are you talking about the distinct, dark line on the right edge and the much wider, darker area that takes up the left 1/4 of the image, both running vertical?
Or, are you talking about the slightly diagonal darker/stripes that are mainly visible in the lighter areas of the image?
If you are referencing the darker, more consistent strips on left and right... those don't look like any kind of artifact that comes from your slide/negative making contact with the glass, anyhow, nothing that I've ever seen.
They look like some kind of shadow...I'm not familiar with the Epson film holders but maybe your problem is coming from that.
It almost looks like you are scanning with no backlight because the label of the slide is casting a shadow onto something there. The darker area on the left looks like a shadow as well. Double check to see if you are scanning in transparency mode.
Those slightly diagonal stripes in the lighter areas? Hard to say..they aren't stepper motor related because they aren't in a horizontal or vertical orientation.
On my old linotype-hell flatbed, there is a small strip of glass at the end of the scanning bed. If that little strip of glass gets covered during a scan, I get strange stuff going on. It's a calibration strip and if your Epson has one, you might look into that. I very much doubt that this is the problem.
Hope that helps.