I have to say, this is a strange one...
I purchased a used set of DPA 4061's (the Coresound HEB version) recently (for which I just ordered the new grids and clips from you) and finally used them for the first time last night. The mics generally performed as one would DPAs to, except that it seems these mics record in mono. Meaning, if you speak loudly into one capsule in a quiet room, you get a L/R waveform that is identical. Not close. Identical. I've used 4061s before, and I know Len matches the caps pretty well, but they could not be THIS matched.
Trying to be sure it was the mics and not the recording devices, I tried a number of different things to confirm this is the case: I checked my R-09HR to be sure it was recording in stereo. I checked it again using the built-in mics - definitely the side I spoke into was much louder than the other, and that was with built-in mics right next to each other. I also plugged the HEBs directly into my computer and recorded waveforms with me speaking DIRECTLY into one mic with the other mic off to the side. The waveforms are identical, to the dB. Similarly, in my recording from last night, the waveforms are matched exactly.
Both mics seem to pick up a signal just fine; it's just that the signal that is output into each channel is a blend of the L and R channels.
I am no expert in electrical engineering, but this seems like a very bizarre result. How could something like this happen? I assume it would require someone affirmatively making a modification or faulty repair, not that, say, you could "bump" something and make the mics do this?
Have you ever heard of this happening before with Coresound mics or other manufacturers' mics?
I've emailed Len as well to see about servicing, but I thought this was a strange enough occurrence that it might be interesting to see if it had happened before.