Answer
This behavior may occur when your file contains a lot of waypoints (or POIs). It is just Windows slowing down as memory fills up. Depending on the number of waypoints/POIs and the speed of your computer, Tyre may seem to hang. It is not really hanging, but it might take a lot of time for the activity to complete.
I recommend to use a maximum of 100 waypoints or POIs for one file. If there are more, split the file, using ‘Split’ or ‘Reduce’ from the ‘File’ menu.