L2P and 6P Compatibility - I need your help

Greetings all,
I have a vintage round-head SF 6P with M61W and McClicky.
I recently acquired SolarForce L2P (blue), and installed NB's NW 3-Mode XR-E Optic.
I also put an O-Ring on the outer edge of the L2P forward-clicky switch, to allow it to tailstand.
I run both on SF CR123 primaries, and both were working great about an hour ago.
I had created a battery magazine for the L2P from a piece of PEX tubing.
I noticed it was a little tight - the batteries wouldn't slide in and out once it was installed.
I popped it out, and sanded the ID and OD just a but.
Put it back together, and it wouldn't turn on.
I swap the tailcaps, and both lights work just fine. Black 6P with blue L2P momentary press and on/off click are just fine.
Blue L2P with black (Z41) tailcap with McClicky momentary press / mode cycle / on/off click are all just fine.
Swap them back, and the 6P works fine, while the L2P still won't activate.
Springs are connected in head and tail, and are plenty long to provide contact.
Any ideas where I should start to look? I really don't want to run them permanently with the wrong tails, and would prefer
to keep the McClicky with the 6P.
Please, I need your help to get the L2P going again.
Thank you.
- Tom

Updated trouble-shooting:
L2P body, 6P head, Z41/McClicky, M61W - no dice;
L2P body, 6P head, Z41/McClicky, NB Optic - works fine;
6P body, L2P head, L2P tail, NB Optic - just fine;
6P body, L2P head, L2P tail, M61W - works great.
6P body, L2P head, Z41/McClicky, M61W - doing fine;
L2P body, 6P head, L2P tail, NB Optic - NOTHING;
6P body, L2P head, Z41/McClicky, NB Optic - doing its job;
L2P body, 6P head, L2P tail, M61W - No Output.

There seems to be some disconnect between the L2P body and tailcap.

tjswarbrick said:

There seems to be some disconnect between the L2P body and tailcap.

Click to expand...

Aarrgh! Nevermind. After all this fiddling about, I lego'ed the L2P tailcap back on the 6P body with L2P head with NailBender's finest - and felt the tail switch flopping around.
Re-tightened, and cranked it down with all my might. Now, both work just fine in their original configuration, so you can ignore this thread.
Sorry. Thanks for reading!
- Tom