The ai-knob lock function does not work with plugins. Not even with padshop or retroluge.
What device with AI Knob do you use? Do you have last version of the driver?
I just tried this with the CMC-AI, it works with no problem.
Strange. I have the CC121, on mac.
If Retrologue didn’t work with AI I would surely have noticed 
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I have a cc121, but you’re making me doubt now. Can’t test just now.
I tested it again, in Padshop, and Retrologue too. It works to mee, on Mac (OS X 10.7.5; Cubase 6.5.3).
Strange. It works for me in VSTDynamics, StudioEQ and cubase internal functions. But the external one the lock does not lock, but the knob it self works but auto select does not. My first guess is that was automap. But automap is not used with padshop. But I have found even more strange behavior. In Halion Sonic SE it works fine. (So even mysic, spector and prologe)
After a reboot the problem with padshop is gone. But lock still does not work with third parties plugins.