Hey Tim,
I've been using the app with the K3 III for some months now and have encountered few issues. Not exactly yours though but here are some things to check on your iPhone:
- Make sure Battery saving mode is **not** enabled. iOS takes strong actions for saving the battery, and this may lead to non-precise location,
- Check in Settings > Image Sync > Location that authorization is set to "always".
The app needs to be launched but it may launch automatically in the background if you use the feature regularly.
Hope this can help.