The first time we encountered it was not setting any time zones in the app. As soon as the a task became overdue the app crashed. There was a specific error message in the logs but that's been lost .

The second time was on a new instance, which occured as soon as you set a time zone. I set mine to Mexico City.

The front end became blank with this error in dev console. No stdout logs.

index-e1a598c6.js:44 Uncaught (in promise) Error: Unknown variable dynamic import: ./lang/<unset>.json
    at index-e1a598c6.js:44:7406
    at new Promise (<anonymous>)
    at __variableDynamicImportRuntimeHelper (index-e1a598c6.js:44:7312)
    at setLanguage (index-e1a598c6.js:44:78484)
    at index-e1a598c6.js:817:112789

Luckily, it seems just to be the front end. I ended up download the vikunja desktop app.