Before sending the cameras/meters out for repair, check to see if the battery contact is the issue. If your cameras all have serial numbers below 77xxxxx, you're likely to have the early style battery chamber which had a tendency to crack and cause the battery contact to become intermittent in function. My first F2 had a dead meter when I got it. Gave it a good whack with the palm of my hand against the baseplate. All of a sudden, the meter started working. That body was pretty early, being in the #713xxxx range. I had another, in the #721xxxx range, which had a wad of rubber cement under the contact, keeping it in place. The rest of my F2's have mainly been in the 77xxxxx-79xxxxx range, serial-wise.
If it isn't the issue, consider finding a few DP-3's and DP-12's that have twitchy meters and have Sover replace the ring resistors with his upgraded part. Then, you'll have the top-level F2 models for both non-AI and AI.
You can check the voltage at the contacts on the top of the camera also. It doesn't take much dirt on those contacts to keep the current from flowing. I fixed a couple of non functional F2 meters just by cleaning the contacts.