REL G-2 Question

I recently purchased a lightly used REL G-2 sub. (This is first sub I've ever owned.) It sounds great but there is one operational issue that has stumped even REL's engineers at their office in California. I do mostly 2 channel music and my system consists of Sonus Faber Liutos, CJ ET3-SE pre, McCormack DNA 500 amp and Esoteric X-05 CD player. My HT system is an older B&K 305 receiver with a Luito center channel. I use the Theater Bypass on the CJ to connect to the B&K so I can get 3.1 Dolby digital when watching TV or using my DVD player. I am using the REL's high-level connections to the McCormack and the .1 LFE connection from the REL to the B&K. All connections have been made exactly to REL's recommended set-up and connectivity directions.

Here is the problem: When in 2 channel mode, the REL's separate .1LFE volume control will actually supply gain to sub when there is no LFE signal! I even unplugged the B&K from the wall. Raising the LFE volume still creates gain! I then tried unplugging the interconnects from the CJ's theatre bypass to the B&K. This does not eliminate the gain either. The only way to eliminate the volume gain from the LFE is to unplug the actual .1 LFE cable from either the REL or the B&K. I can, of course, set the LFE volume to Zero and control the sub's 2 channel music volume through the High Level volume control just as it is supposed to work. It bothers me though that the sub is performing in manner in which it was not designed to perform. I've talked to dealers and to REL's engineers on the phone and no one can figure out what's happening. They all state that they have never heard of such a thing and that it seems impossible. One said it sounded like cross-talk so I made sure none of the cables were touching each other and made sure no bare wires were touching each other.

In closing here are my questions: (1) Do any of you know what might be happening? (2) If any of you have a G-2 (or G-1) would you mind turning up your LFE volume while in 2 channel mode with a similar LFE connection and let me know if you get the same result? (3) If the sub performs flawlessly in all other areas is this even worth worrying about given that I can just unplug the LFE cable when listening to music? BTW: The seller has offered a complete refund if I want it.

THANKS!