T-Online and CalDav/CardDav

Hello,
using eMClient for a while now coming from MS Outlook…very satisied …but have an issue with T-online CardDav/CalDav as follows:
I have create three accounts for t-online : mail, calendar and contacts as i was not able to do it all in one (as it was possible for my gmx account)
Anyway - sync works well exept when starting eMClient, i receive a “Password required for Calender T-Online” …with credentials filles out and it works when just clicking ok. Sometimes when the PC is on for a longer while, the PW request window pops up again.

Synclog does not show a similar error.
Now the interesting part :
The PW required message appears for the last account in the sorting, e.g. : if sorting is calender - contacts, i get the Message for contacts

Seems it is a kind of “limited request per time” issue - but did not find a way to set the sync intervall to different times - any ideas?
btw its a t-online free account - but it’s the same for my gmx account
greets