Why does unplugging/replugging TT leads from tube phono pre-amp reset dead channel?

I have spoken to Victor several times.  He is not sure the problem isn't my TT. Or the leads. 

Thanks for the suggestions. I have a Linn LP12. Only one set of RCA leads. Can’t remove them.

Al- I’ve had the unit for years. This is a new issue...I think...perhaps since the upgrade to the Superpak. BAT can’t replicate the issue.

1- I have the shorting plugs.
2- not sure on the loading...it was set when the cartridge was put in years ago.
3- no sounds...no clicks....It just gets quiet. I can listen for hours before that happens.
4- " When it powers up, it will not be working." That is after the initial mute has concluded it’s cycle. I wait. I hear the click that it’s on. I get music on one channel and I hear nothing in the other channel. I just pull the dead lead, put it back. I’m good to go.

Think it’s a grounding issue? It switches from one side to the other randomly. Does that info help? Thanks everyone.

Hi Al,
OK...here is what has happened since your post:
 - I own the adaptors you suggested...supplied by David Lewis Audio upon sale.  They have been un-used out of a concern that it would degrade the sound.  But you provided reason to use them.  (FWIW -  I did not do the tests you suggested.  Is there need for that still?  I do not want to overlook anything....)
- I inserted the adaptors prior to powering up...and both channels worked!
- I listened to a few albums...and then the right channel dropped out...
- Without muting anything...I unplugged the right channel from the balanced adaptors and immediately plugged it back in..and the channel came back!
- and I took a swig of gin...b/c I was stymied!!!  HELP@@!!!

Hi All...
Lewm -- the male end of the Linn RCA is split, so I gently expanded it...that was a while ago in response to advice from a dealer a few months back.  It has not helped.  Length, though, I cannot change.  I have considered upgrading the cable on the TT.  It might resolve issue. I cannot believe the adaptors also have the issue with the Linn cable.  But who knows.  Thanks.

Al -- I will try that test next time the issue presents.  Thanks.  As to opening the phono stage...that will be done over the weekend...as it has 14 zillion screws and is a major hassle to open.  

Uber -- BAT had the unit in for an upgrade (superpak) and new tubes...the issue existed prior, I believe, and they could not replicate it. (Which is why they say its my TT, not their unit. However, I have another phono preamp...and never had this issue with that unit.)  I don't have access to another TT...but that is worth pursuing.  Especially if I can get it to happen with a different TT!  Thanks for the suggestion.

A mystery.

Joe

Good news?   I have not been able to replicate the issue of late.  Perhaps this post will remedy that. I've ordered from Amazon a tube of DeOxit. Just in cast that's the culprit.  Next steps are to check loading on cartridge.  Suggestions on loading to address this issue? It sounds fine as it's currently set.  Also...will be interested in seeing what else I discover with the hood open. 
Lewm- The male RCAs from Linn simply screw open- very easy. How do I know by visual inspection if there is "an intermittent or cold solder joint to the hot pin."  I'm not sure what that means. Thanks. 
Thanks all.  

As expected...it couldn't last.  So the left channel dropped after a loud passage on Chet Baker's Chet. Great morning tunes.  I spun the plug.  Wiggled it.  Wiggled near the TT. Nothing. Pulled and replaced.  Channel returned.  I visually inspected the insides of the plugs...the solders look solid.  A bit of oxidation inside the ground part (inside the outer part).  
Thanks for sticking with me on this. 

Joe

Hi All,
Thanks for your patience with the silence during the holidays.  I have a few things to report.
- First, I'm grateful for the suggestion to look at the load on the Shelter 901.  The recommended loading is 100.  I had it set at 47K.  I dropped it down from 10K, to 1K, to 100.  Seems to balance the treble/mids so much better...but also, the dropouts seem to have stopped.  This may have been the cause of the issue, Al.  Thanks.

- I also examined each tube carefully.  One of the 6N7Ss had a hairline crack on the base.  I replaced it.  Could this have caused BOTH channels to be randomly dropping??

- I have been listening all week...and the drop out occurred only once after those changes.  I did notice a big dustball on the stylus.  Removed it, did the unplug/replug...and no more issues.  Could that be a factor??

- I appreciate the LP12 support.  I like the table...other than the click in the bb at the bottom of the sub platter spindle. ( I can hear it on very soft passages or before the music starts.)  I think in your situation, the MM change from MC might point to Al's solution.  

- I don't know what a cold solder crack would even look like.  But the Phono preA was at BAT about a year ago...so I assume they would have noticed.

- The system sounds the best it ever has.  I'll keep you posted.

Happy New Year.

Joe