I have moved the cables and the problem did switch to the other channel. I even tried several other rca cables to eliminate bad cables as the possible culprit. The BT is new. I was having the same issue with another BT, that's why I bought a new one. Only to be incredibly frustrated it happened again. I'm just taking a shot in the dark of it being a grounding issue with the BT. It just points that direction when it does just fine on an input (cd) which doesn't share a common with other inputs
If you had the same issue with a different BT receiver, it's not the BT receiver.
Connect the left channel's cable to the Left output on the BT receiver- if it works, move it to the Right channel. If it works, try this with the Right channel's cable- if it doesn't work on either cable but the BT receiver send signal out of both channels, it's not the BT receiver.
Plug the cables into the Technics amplifier and set it to that input- raise the volume control to about 9:00 and touch the tips of the RCA plugs- you should hear hum from each channel.
"Too weak"? If the level is similar to that of the other sources, there's no "too weak". Line level for sources is basically the same across the industry- if you can hear it, it's OK.
What cables are you using? Are the plugs extremely large and is it possible that they're crowding each other? If that's the case, especially if each channel works separately, it's possible that a connection failed. I have seen cables with the tip pushed in and some that lost the tip. Have you tried using the same cables with your CD player?