first of all, thanks for creating (and especially maintaining) all of these applications here. Good to see quality products from an Austrian company.
I am using ICSdroid to sync calendars from teamup which is working just fine. However, once a day one of the ical feeds fail to synchronize properly (which is non reproducable), so basically there's just a error notification without any real impact. A suggestion to improve that would be
a) automatically close a notification if the repeated attempt succeeds
b) add an option, to just show a notification after X failed attempts. So for X=3, it should not show an error after the first or second attempt, but after the third failed attempt. It would add some delay in case of a real error, but it would prevent random non-reproducable errors.