Try from the console. If you can login and request shell there, you can change the default shell away from apliancesh to bash.
I just tried the management https://xxx:5480. I could login and saw the screen for a split of a second but returned to login window with "Session has expired. Please login again."
From console, if I understand correctly, after entering "Troubleshooting Mode Options", trying to change "Enable BASH Shell" by pressing "Enter", I could see a window show up in a really short period of time, then immediately gets me back to the "<F2> Customize System" Login window.
You've got something very strange going on as this is certainly not normal operation. It almost sounds like a networking issue in your environment. You may want to open a case with GSS to get to the bottom of it.