IQ datafields crashing (caused by fit contributions?)

Yes, this was also discussed here. It's possible your data field was installed and then used for months without problem, then they install another data field, and suddenly your DF starts to crash...

There's not much you can do about it. You can't catch the error, you can't check in advance if the limit was exhausted. You can write some FAQ about it where you explain the problem, and that removing other data fields that write to the fit file can fix the problem.

The only other way I can think of improving the situation is to add settings to your data field where the user can enable/disable which fit field to write, thus being able to enable those that are more important to them and disable those that they can live without. If they're lucky that's enough and it won't crash.

Yeah for example, a support article for Stryd Zones (a data field which writes many FIT fields) suggests removing all other CIQ data fields from an activity that uses Stryd Zones (without elaborating).

It's kind of a bad look for Garmin imo, as it suggests that devices can't handle multiple Connect IQ data fields in an activity, even though they allow you to add multiple CIQ data fields. And it's really not too far from the truth.

At the very least it would be nice if this was a catchable exception. Not sure what the rationale for making this a fatal error was: is it out of necessity (i.e. for technical reasons we aren't privy to), or is there an assumption that FIT recording would be an essential feature of any app that used it, and therefore there's no reason to do anything but terminate the app.

Imagine if iOS or Android crashed if you added too many widgets to your home screen, to the point where the average app store description says "don't bother trying to use other widgets at the same time"? Yeah, I know it's not really a fair comparison, but I doubt the average user would care.