Continued misadventures with Ortofon 2M carts

I posted a while back that the Ortofon 2M Black cart lost left side gain while playing on my new Denon DP 3000NE. I checked connections, played it directly through the phono stage on my amp (Cronus Magnum 2) as well as the phono stage I use (Parasound ZPhono USB). No joy. I swapped it with an older Ortofon 2M Blue. Same, left channel barely there. Also have a Grado Gold. That one played both channels, but with an audible hum. 

To update: I got a good deal on a Denon DL103R. That one plays beautifully. Both channels fine, no hum or buzz. 

Because the Ortofon 2Ms didn't really fit into the Denon head shell, I bought some generic head shells that were completely flat, & fitted the Blue & Black into them. Now it's the other side, their right side, on both of them (they're different brand head shells) that lack gain. (And the Grado Gold still hums). 

One of the generic head shells is clearly a poor fit for the tonearm because it sets with an uncorrectable wrong azimuth. The other lines up okay. But I get the same symptom with both. Can anyone make any sense of this?

Andy y