When fast-traveling via the map after grinding some meseta out in the field (and using the quick-sell-item option extensively), upon arrival your meseta will roll back down to what it was before you started.
The one to notice this was my friend, at first they thought they were seeing things, then they certainly made sure it was happening, and finally I managed to shadowplay a clip of it happening from their discord stream since they don't have access to Shadowplay / Nvidia Share.
The clip in question is uploaded to a google drive here.
From the clip you can see them teleport from the Labs back to town after running through it for another good while, them opening their info screen before and after the TP, and upon arrival their Meseta has gone back down to around 2k from around 24k.
-No, the meseta did not automatically get transferred to Meseta Storage, it was empty each time they checked it.
-The meseta did not come back even after re-launching the game completely. Once it's gone, it's gone.
-The clip has not been edited in any way other than muting the audio and cutting off any irrelevant footage before and after the clip. No video has been cut from between the start and end of the video itself.
Now that I know this is a thing, I must admit I feel like I've been arbitrarily losing meseta every now and then even though I could've sworn I didn't do anything with it in-between, and this might be why.
I stronly advice people to constantly monitor their meseta count and take a shadowplay clip if they notice any discrepancies or want to double-check nothing's happened to it between switching areas.
In case you do notice something, please submit your findings not only to SEGA but also to this thread. This needs to be fixed ASAP and any meseta lost to be reimbursed to the players.
My guess is that whatever meseta you earn through the inventory quick-sell button just gets deleted when you fast-travel for some reason, the little meseta you get as drops may or may not be affected.
As to what causes this bug to happen in the first place is unknown, maybe a combination of things including the huge lag spikes we still have even after the last maintenance.
Keep an eye out, tell your friends and your alliance members, get this info out there so that other players can start looking out for this issue as well and lets hope SEGA fixes it soon.
It sucks to lose a whole day's Lab meseta grinding progress just randomly when you fast-travel back to town.