I actually have the same problem with my S5 using UM PVA but I think there is a second issue of excess oozing as I notice a fair bit that comes out of the nozzle between nozzle switching during print. I hope we both can get some answers. This is material straight from the bag and in the printdry for several hours before print and during the entire 13 hour print time in my house which is about 36% humidity.