[TPP]can’t keep mechatronics specialist?

I’ve replayed the mission (10 - Angels with Broken Wings) and extracted him several times and he never joins my staff. I saw a post saying to develop what you need or check for him during the mission after a checkpoint but that didn’t work either. He wasn’t there immediately after extracting or after the checkpoint or after the mission. I’m losing a bunch of money replaying the mission over and over for nothing. Are there any tricks to this? Thanks.