Please do the following test :
1/ set BAM in Relay mode, MIX full left (dry) and ACTIVE off
2/ send a 0 dBu sine to the aux send, set the aux return (or line) channel to 0 dB gain and fader
3/ on your patchbay, plug the aux send directly to the aux return (or line) channel. Check the level (should be 0 dBu)
4/ plug the BAM back and check that you get the same signal, when ACTIVE is on or off
If you have a loss as soon as you plug BAM, how many dB ?