You can report the error right on the main overview via the "leave feedback" symbol that looks like a smiley face. You can find it in the bottom row of each HitApp tile. Click on it to open a context field where you can then define the issue further from a list and also explain your problem in your own words in more detail.
If you are already in a running training, qualification or HitApp you can find this very same option via the link “Report a technical issue”, which is located in the upper right corner of your screen.