CalDav+Server+Issue

I am getting error messages when em updates I think my contacts file. I get a “bad request” reason for the issue. I have included screen captures of the log and the error message 

Hello Peter,
what version of eM Client are you currently running? Can you check in Help>About section?
As for the error, try resynchronizing your yahoo Contacts folder by right-clicking the folder>Properties>Repair. Run the repair and wait until the synchronization finishes and let me know if the error pops up again.

Regards,
Olivia