You pretty much described what my keylab 49 started doing after flashing firmware 1.24 for keylab 49
While I can't offer any solution, at least it's now two of us.
I would like to return to shipping firmware 1.18 if it was available.
I have my keylab 49 connected directly to my MacBook pro retina, no hubs in between.
EDIT: Since using MIDI Control Center and setting to defaults, sending that to the key lab, storing it to setting 01, and then fixing the few odd things of the default (Filter A and AMP S used the same CC (Gave Filter A a new one) and the pads are set to toggle (switched to midi note)), saving that to a file and sending the setup to the keylab and resaving to setting 01 on the keylab, it seems to behave normal, the loop and play/pause buttons also stay off so far)
I only used non arturia VSTi today, but it's still noteworthy it's behaving since it was acting up in Analog Lab as well as all other VSTi.
P.S. i wonder if this now should all be moved to the hybrid synth/keylab forum that now exists?