Sounds more like a hardwareproblem rather than software issues.
Maybe a loose cable or two, and/or bad solderings?
Take a look inside the T4 to see if here is some tips & hints to help you out:
https://www.youtube.com/watch?v=iaxE4i9x_S4

... or if there is a dealer / repaircenter near by to ask for help?
Good luck, T4 is a great keyboard as long as it work as it should.