I ran across a post from Marti1038 that was posted in 2019 about motor vibration problem he was having with a 3hp baldor motor with a kbac 29 vfd at lower frequencies. I'm having the exact same problem with the same setup. Motor vibrates and chatters at 30 -40 percent but runs fine at higher frequencies. I tried adjusting the trim pots and checked all jumpers and connections to no avail. I tested vfd with a 1 1/2hp baldor motor with settings for that motor and vibration and chatter wasn't as bad, but still there. like the original poster, my motors are new old stock I've had for a few years. The grease is good and the shafts turn freely without any glitches or bumps. Was this problem solved, or do I have a bad vfd.