Thanks for all the replies and input.
This engine doesn't kick back all the time but just once in a while (maybe on the compression stroke?).
The piece(s) of info I was looking for was:
" - If exhaust valve does not open more than 0.06mm (0.024in) briefly just after intake valve closes, ACR mechanism on camshaft is faulty."
If the highest compression reading is less than 71psi, I'll need to trouble shoot the engine.