Linux Desktop Client 2.5.1 GUI crash

hello together, since a few days the desktop client is not working properly, I can not log in, the window is no longer displayed correctly. When trying the connection again and again, no login possible, because no input field
Unfortunately, I do not know how to continue.

System: LinuxMint 18.3 Cinnamon 64bit
Cinnamon-Vers. 3.6.7
Linux-Kernel: 4.15.0-43-generic

Thank you very much