The branch locations have their own Citrix setup.
So local storefront, controller and Citrix servers. The Site database and WMS are hosted in the central datacenter.
The thin clients in the branches connect to the local storefront server, so only local traffic, no wan connection.
I pointed one of the thin clients in the local branch to the central storefront server and the issue is gone.
Whe have UDP enabled for the Citrix sessions.