something permanetly reset my email accounts from installed mail applications (Samsung Note II stock and Gmail app) I've met with a very annoying and strange issue regarding email applications on my Samsung Galaxy Note II. My search in Google across multiple Android forums has has not given any result. I used for about a year on this device Samsung's stock email application to work with my mail accounts at some local mail servers and Gmail server. Also I used Gmail stock email app to work with my several Gmail accounts (some of them are the same as in Samsung's stock email app and some are different).

One nice day several weeks ago I've suddenly disclosed, that all my mail accounts in the both apps are totally removed, that is all accounts settings and data (incoming messages loaded in the local cache, my drafts etc). When I called any of these two app, it starts as the very first time, that is offers me to configure any account before I can start using the app.

Futhermore, the default Google account in the general stock settining ssof the account has been removed too.

I have restored all accounts in the both apps and the default Google account in the device`s general settings. But several days later I've suddenly found out, that the both apps had reset and were empty again. Well, I've configured them once more... and now they are empty again.

I suppose, that this issue is very probably conncted to the fact, that I use the same Google account as default account on two different Android devices, that is Samsung Galaxy Note II and LG G-2. Well, I have read here at the forum many different topics with the same questions, whether it is OK to use the same Google account as a default one on multiple devices, and the answer was always "Yes, without any problems". But seems, that the matter is not so simple. Anyway I can not imagine any other reason for such strange behaviour. Furthermore I suspect, that the problem occurred the first time after I've bought and configured my second device LG G2. I'm not 100% sure, but it seems to be so. 
What seems to be essential, all data and setting of these email accounts on my LG device is not affected any way.

Are there any ideas how could I detect and fix this issue? It is impossible use my Note II this way.
Many thanks in advance!
Well, like the other forum I would also say there's just no problem with using two or more devices over a single gmail account. I remembered you said that "local mail servers and Gmail server"data gets deleted. I think that might happen because of something else i.e not related only with the gmail account. Do one thing try factory resetting your device and then try putting the gmail account back in place and see if that again disappears or not! 

PS: Make sure you backup your data before moving forward with the factory resetting.