Is your FM tuner affected by interference?

I have a Magnum Dynalab MD90T tuner that seems to be affected by, what I think is, atmospheric interference. It seems that when the sun is setting my signal strength goes down. I have noise that doesn't allow listening, and it doesn't matter what antenna I hook up. I have had a Fanfare whip, an amplified antenna, and now the Godar, which gives me great DX capability, and nothing cures the problem. It only affects the college stations at 90.7, 91.1, and 91.5. I live on the tallest hill in the county and the stations are 10 miles away. One xmits at 10KW while the other is at 5KW. They both peg the signal strength meter at 9, while the station 60 miles away is at 8.

I recently had the unit back at Magnum' for repair and they found a bad F connector along with a bad multi-path chip. It came back and it sounded better than it ever did. It has performed flawlessly up until yesterday when I noticed the 90.7 station had the signal strength meter bouncing up and down with the multi-path going up when signal strenth was down. Normally, I have no multi-path. I call other friends for radio checks and they get good, clean signal with no noise while I suffer.

Should this unit go back to Magnum Dynalab or do I have other issues?