Pro Power Kit V3 kills indoor chime

Hello, I just acquired a Ring Pro V2 doorbell. All the "ring" stuff works fine, but my indoor chime is now INOP. This is the second Ring. I returned the first to Amazon for this same issue; figuring that the doorbell was defective. No luck, second one behaves the same. I hooked up my good Fluke multimeter to the back terminals of the Ring, and see about 20VAC. When I press the button on the Ring, that voltage goes down to zero for a moment. So the Ring is closing the connection. Here's where it gets weird. If I disconnect the Ring and put it aside , the chime STILL DOESN'T WORK. Huh? So I disconnected the "Pro v3 power kit" at the chime, and then it works ( by touching the wires, ring doorbell still disconnected ). So somehow, the power kit is disabling the chime. The chime is a bone-standard "ding-dong" unit. Made by Desa Specialty Products. It doesn't appear in the compatibility list, nor in the "not compatible" list. What to do? What's inside that power kit, anyway? I suspect it's mostly protection from inductive surges from the chime.