The vertical streaks are caused by normal wear and tear of the drum assembly. You can replace this part for under $25. It should last about 12,000 pages and just replace it once it starts to degrade again.

https://www.amazon.com/Z-Ink-Compatible-Replacement-Intellifax/dp/B00MGUTN9G/ (Drum unit only)

https://www.amazon.com/Z-Ink-Compatible-Replacements-Intellifax/dp/B00MH1P49M/ (Drum unit + 2 toner cartridges)