If TOUCH mode is behaving erratically on your UltraNova then you should ensure that you're running the latest firmware on your Ultranova by connecting your Ultranova to your computer and running the latest Ultranova installer which can be downloaded here.
It's also important to know that the unit calibrates the touch sense every time the unit is turned on. If any encoders are touched when the unit is booted, the calibration will be set incorrectly.
To ensure this does not happen, make sure you do not touch any of the encoders while the unit starts up.
If you encounter any issues with touch sensitivity after this, please contact Novation Technical Support via the "Contact us" link at the top of this page who will be able to help out further.