If I understand you correctly, you now want to discuss the handling of possible CalDAV related syntax errors and not problems related time limiting barriers during the sync process?!
If so, the usual process is to reduce the problem to a as simple item as possible and to provide detailed information about the used Nextcloud and app version and a simple example ics file which describes the problem with e.g. the RRULE tag. It isn’t purposeful to mix-up several things except you want to have a nice chat about this and that.
So, if you’ve already analyzed a problem and know the root cause of it, you should open an issue ticket, and follow the issue template by providing detailed information to reproduce the problem. This is the only way how the developer can reproduce the problem and enables him to fix it.
BTW, if there are syntax errors in an ics file, why should the server be responsible for fixing it and not the sync tool?