I have noticed that jabref starts to use the computer memory in some extensive ways. I have a 1.711 kB library and jabref uses 2.526 kB of memory. Even firefox which uses memory exorbitantly, reserves only 546 kB. Besides having 16 GB memory, there is no saving and retrieving of memory. However, the computer has becoming very slow with the JabRef_windows-x64_4_0_0-dev–snapshot–2017-04-24–master–4e25cc642 snapshot. Therefore I reverted to 3.8.2. The memory reports are, however, from 3.8.2. usage. Any comment?
A cause could be in when you open files with Jabref. Each time you do it, then the operating system installs a new instance of JabRef in memory. Something is wrong of course, it should not be in that way.
I have only one instance of Jabref due to Options->Preferences->Advanced->Remote Operation clicked.
Therefore, what you wrote, is definetely not the case in my settings.