Hi Halibutt,
Wikimedia Labs, the infrastructure that Wikimetrics is running on, is having some stability issues lately. That might be the problem, and we don't know when the problems will stop unfortunately. However, you can report problems here, but as Jeremy says you should be as descriptive as possible:
1. What did you try to do? What steps could someone take to do the same thing and hopefully run into the same problem?
2. What happened when you tried to do something? Again be as descriptive as possible including pasting in any error messages or screenshots.
As the Support page suggests, the way to file issues is to add something to Phabricator, our issue tracker.