Which version of the Dual Extrusion do you have: Old or new door? this shows how the new door looks like: Replacement Kit for Dual Extrusion Module (VAT Incl.) - Snapmaker EU
If you have the old door, you may have problems with heat creep - see this thread: Dual Extrusion Head: Heat creep discussion thread - you in this case should contact Snapmaker support to see if you’re elegible for a free new door.
If you’re already on the new door, it is most likely your print settings - which temperatures do you use?
PVA seems to be prone to clog the nozzle when getting too hot, recommendation is to stay at the lower end of temperatures.