I called Roy Hall at Music Hall. He said what I was experiencing was not normal and sent me to Mitch Singerman in LA to look at it.
Mitch heard the distortion on the turntable. We took the record and played it on his Goldring turntable which is using a moving coil cartridge (can't remember which one, but he said it was a $1500 piece). No distortion at all. Sounded great on inner grooves.
Mitch tried replacing my arm, stylus and cartridge with new stock of all the same brands (Pro-Ject arm for MMF 5, Goldring 1042 cartridge and stylus). The distortion was STILL there.
We then took the record and put it on a DIFFERENT record player of his (Rega) which was outfitted with a Goldring 1012 cartridge. THE DISTORTION WAS THERE.
Mitch is reluctant to say it, because he said he always found Goldrings to track very well...But it's evident to me. Goldring can't track inner grooves well. At least not on rock music.
Now...When we FIRST tried out my turntable, I did not bring any of my own records over. I figured Mitch would have some. All he has, however, is classical music. We didn't really hear my problem on those records.
But when I brought over some rock records with more aggressive midrange from guitars, and generally just more loud and "busy" sounding than classical, it was evident.
So I think the Goldring can maybe handle some things well, but loud rock on inner groves? Problematic.
So, I'm now gonna finally try an entirely different cartridge setup. I was thinking the ORTOFON BLACK. If anyone has suggestions, please post them. I am looking for CLARITY at this point, above all. I never want to hear distorted grooves again after all this headache! (not to mention about 5 round trips back and forth to Mitch's place, a good 30 miles from me each way!)