First of all KUDOS for realizing that an amplifier can only amplify what it can see, it's not a miricle worker and it's amazing how often that's missed.
It's interesting that your VHF only channels have dropped off when the Sensar is in-line and that's a little concerning. It's certinaly possible that the Sensar has no or negative gain on VHF. This is obviously not a connector problem and I'll look at the output of mine once I get back into the LA area where I have a good selection of VHF to look at. It certainly should not do that but everyone has put all their attention into UHF, thinking VHF is dead. That ain't the case
BTW- it's also possible that you have strong TV or FM transmitters nearby (?), and those can easily swamp the Sensar amp. Don't forget you are driving one amp in the head into the Sensar's amp. Not the bast thing to do anyway, but gaining up an already swamped amp then overdriving the TV can get ugly.. I have this problem at one of our camp sites