This is by far the biggest issue. Really there should be a warning in the app about this when you’re getting close to the limit. I talk too much about being made homeless in Tokyo by my bank, but the truth is this limit could cause the exact same issue for a Mondo user, and it’s not documented anywhere.
Granted, “carry a backup card” applies as always, but what’s less obvious is that once you’ve loaded funds on to your Mondo card there is no easy way to transfer them out again to the backup card’s account. So “don’t load essential funds onto your Mondo card” also becomes a necessary warning.