Hi @Jnyberg,
Are you using the servo_n_min/max_momentary button functions? If not that may be the issue. If not it may be a controller specific thing, in which case hopefully @etienne has some idea what’s going on 
@EliotBR @etienne Yes I am using the momentary buttons. But they just open/close the gripper fully. There was other options I tried too that didn’t work since momentary is what I would expect to be the one to work.
Update: I added an extra button with the assignment servo_n_center and that allows me to stop the gripper at its current position. So I am able to manually start and stop it in either direction when I please, but this is a very inefficient and inaccurate process with three buttons compared to the other controllers using the momentary feature with two buttons. I am wondering if there is no option for momentary assignments on this HCU for the buttons and only for the dials?