I recently downloaded the BTS wallet client on Win 10 on a new machine, and restored using my .bin file and then set a password. When I regained access to my main account, I checked and saw many, but not all of my sub-accounts. To my understanding, all of these sub-accounts have their keys derived from the brainkey in the main account. Is the .bin file my brainkey?

Later on, without doing anything differently, I suddenly see some of the missing accounts, but then some of the accounts I saw earlier had gone.

Any idea what causes this, and what I can do to fix it?