I know you had said you verified fluid level at least twice and right down to the ounce or decimal point as I recall.
How is fluid level checked/regulated or maintained on a T56? Does it have a fill level plug like on some gear boxes or rear differentials? The kind where level with the plug is "good" to ensure gear submergance which relies on the gears to carry lube up from there? Or are they filled near the top with minimal air gap?
Forgive my ignorance, and I have not read your whole thread yet either.
On a DIY problem solver level, as a last resort if everyone blames your T56 as being an odd ball for not venting right... I was wondering about an additional vent originating right in or on the shifter also. Granted that is not part of the design and won't bode so well for a return credit.
Machining it would be a breeze, but again not with a pending RMA#.