Package: x2goclient
Version: v. (Qt - 4.8.7)

To reproduce:
  1. Create a new session with type Single application and set Command to "Firefox" (with first F in uppercase). Click OK to save it.
  2. Choose "Session preferences" to edit the session.
  3. Set Command to "firefox" (all letters in lowercase).
  4. Either click OK to save it or just click to focus on some other field.
  5. The Command changes back to "Firefox" (with first F in uppercase).
There seems no way to correct such misspell. I had to delete and create a new session.