I had a loop in the declaration of a template which involved a while-loop that were to terminate once a variable increased beyond a certain value. In my haste I forgot to increment this value, and as a result, UPPAAL became unresponsive.

I suggest to implement some bound on the number of iterations that are tested, or an upper limit on the amount of time some code are allowed to run before UPPAAL stops checking it. This allows silly users (like me) to get in trouble. The problem is that there is no indications of the problem, and the user will need some knowledge of how UPPAAL works in order to find out that the code is the problem.