Non-pilot managers who treat their folks like shit. No respect for time-off/OT/etc. Ground job BS. Getting stuck on the SW Border with no chance of transfer. Forced into UAV operations without a ramp back to the cockpit. They can chest beat about "Mission before money" all they want, just like the Navy does, but people are leaving for the same reasons they left Active Duty.
We've got two CBP P-3 types in my reserve unit and their main complaint is how much P-3 hate there is at the higher levels, and the culture clash between the former Customs and BP air branches. According to them a lot of the leadership grew up in BP and are very Army-centric and dismiss the utility of the P-3 types ignoring the drug totals the P-3 guys interdict, fixating on helo ops and the border where much smaller loads are interdicted, and are very shortsighted in their planning for air ops and the aircraft fleet as a whole. They did say the forced UAV thing has gone away for them, for now.
They had some interesting insights to the poly as well, and CBP's policy there doesn't seem to match up with best practices.
EDIT- I have to amend the UAV claim after talking to the CBP folks for a while about CBP stuff (it was a boring exercise, lots of BS'ing), they apparently aren't making more P-3 guys go UAV's now but some who were dual-qualed still have to do their UAV penance regularly. They are apparently trying to build up a dedicated UAV cadre and the dual-qualed folks will have to do double duty until they are full up on the UAV side.
The two caveats to that for the new hires are that there are only 5 basing choices right now for the new pilots, 2 or 3 are UAV bases and the others are helo bases with no new-hire pilots going directly to P-3's (sensor operators can still go straight to P-3's). The other caveat is CBP air leadership wants to move away from UAV's, apparently the juice ain't worth the squeeze. Whether or not their bosses and bigger leadership goes along with it remains to be seen.