Found another serious defect. This one exists in both Poser 11 and Poser 13.

Create an animation with layers. In the second layer, set it to "add". Choose "Current layer only". This should zero the figure. Grab a body part like an arm and try to manipulate it using the parameter wheels. You'll find that the parameter dials are completely bugged and you cannot do any controlled manipulation using them. Only direct manipulation works. You can't even type values into the parameters and have them behave as you expect.

These are the types of bugs that I keep hoping get fixed with subsequent major versions but never do.