Apps crashing on macOS 10.15

Recent updates of BusyContacts and BusyCal (v2024.3.x) are crashing for macOS 10.15 users.

This appears to be due to a bug introduced by Apple to its developer tools. It seems to have caused the app to become unusable on older macs. We're looking into this but if a resolution is not found, we will have to discontinue support for macOS 10.15 altogether.