JabRef version JabRef 5.0-beta.382--2020-01-28--0b53d4b on Ubuntu 18.04

• I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

Steps to reproduce the behavior:

1. Open watson.bib.txt in JabRef on Linux (can't reproduce on Windows)
2. click on the file-button of the entry
3. choose the second one
4. File opens (The file must exist, otherwise the problem does not occur)
5. Mouse moves, but clicking does not do anything and keyboard also does not interact, but computer sill runs e.g. Systemmonitor does still update graphics, but does not interact with input (all programms cummulated: 30% RAM-usage, ~5%CPU usage)
6. ssh to my PC, and kill JabRef
7. everything works again, JabRef gone. (25% RAM-usage, ~5%CPU usage)