1.5 Pierburg Carb reluctant to start when warm

Starts fine when cold with auto choke set. After driving for a while and getting warm, if I stop at the shops for twenty minutes when I try to start the still warm engine, it struggles. No autochoke set as it's warm but I need to goose the throttle to get it firing.

Any ideas what may cause this, probs fuel related but no idea of its too rich or too lean, etc.