Changes sometimes not being reflected

We’re using the contentful.csharp NuGet package version 4.1.1 in our ASP.NET MVC5 web app. In 99% of all cases everything goes well, but from time to time we’re experiencing following problems:

a) changes on content (f.e. text) are not being reflected, both with Delivery API and GraphQL.
b) sometimes (smaller chance) content (text) changes are reflected but only the first TWO characters of the whole text will be served (both Delivery API and GraphQL)

Could a SyncInitial() overcome those troubles? I doubt it since in the tutorial ( only .GetContent() is used and not SyncInitial().

I know that the delivery API is backed by a CDN with a potential delay of 5 minutes. But when this problems occur they last “longer” aka endless. When i unpublish the content (and yes, the changes were published and not “draft”) and re-publish it again, everything works again as it should.

Has anyone made the same experience? And what could be done to overcome this?

got answer from support.
problem is related to CDN cache.
support is aware of it but no ETA.