I just found out (with many trial/error Git Checkouts) that the recent update of Xamarin.Forms Nuget package from 4.6.0.847 to 4.7.0.968 creates a consistent crash with my SfListView RightSwipe context action, both in simulator and on actual iOS device (couldn't test Android).
The crash isn't even captured by the debugger - the App just stops completely without any notice.
After downgrading back to 4.6.0 (with SfListView still at 18.1.0.59), it works again. Other SyncFusion elements and the SfListView itself including Drag&Drop reorder still worked under 4.7.0 - only the rightswipe caused the crash.