vCloud Director upload to catalog fails

Hi,

I have an installation of vCD 5.5 where I can't get the upload to a catalog right.

Every upload (tried several browsers) fails on the initialization-part with a 'Failed to connect to host <ip of the vip> on port 443.'-popup.

CA certificates are installed correctly in the cells, VCD public REST API base URL has the value 'https://vcloud.mydomain.com'.

My cells are behind a F5 Big-IP 3900 LB, with SSL-passthrough for the HTTP-part to the cells.

For troubleshooting, I am able to upload if I go directly to a cell, bypassing the loadbalancer.

Vcloud-container-debug.log is telling me nothing, no errors or useful information there.

Anyone who can help me out on this?

TIA!