Are some tracks impossible to track?

Analog playback is full of compromises. Even assuming proper set up, different cartridges and stylus have strengths and limitations and the ability to track a highly modulated groove is one of them, and perhaps the most common. Some of the best sounding cartridges don't track worth a crap (so to speak) and some of the ones that can track everything sound like crap. And, as in the case of the Pollini disc its hard to tell when its your cartridge or the recording itself. Those DG's were not SOTA recordings and Pollini is not noted for a warm enveloping sound.

Set your cartridge up to sound its best for the 99% and accept its limitations.

Oh, I forgot to mention, that the VTA (SRA) can also effect the sound and give the impression of distortion. If you have set the arm/cartridge to optomize for thick audiophile recordings and then play thinner disc's such as the DG you may bechanging the angle of the stylus in the groove just enuf to exacerbate a tiny distortion in the recording, one that you would not have heard but for the inappropriate VTA. Many folks completely overlook the importance of properly set VTA for each recording, or at least for the thickness of each disc.

The JMW-9 is not a particularly good tonearm so it is not unusual for occasional mistracking.

Newbee may be right, but my rig is not that much different than yours (Aries with JMW 10) and I haven't had a tracking problem with 3 different carts and a wide range of settings and adjustments. Also any of the three carts I've used lose dynamic range and sound boring when run at max. weight, and I've never tried any max. weight above 2.3 gm. Since you've already triple checked all set up parameters, I wonder if you were unlucky and bought a lemon blackbird or scale? Also,if you had a microscope or maybe just a magnifying glass and could get a real close look at the tip of the bird, there may be something going on. I have had tracking problems when a very fine thread got wrapped around the stylus on a different table, sounds obvious but I couldn't see the durn thing till I took off the arm and got it in some real good light.
Good Luck!

Fair enough. I have reversed back to 2.2 g VTF.

But the JMW 9 is not that good OK, I know its not a $2-3k ARM. Is that what it takes? I thought the JMW 9 was designed for the VPI tables. And it does track 99% of what I listen to fine, as far as I can see. Maybe when the cart breaks in all the way the suspension will loosen up and it will track just a tad better. Or maybe on to the JMW 9 signature!

What are the best tracking carts out there?