I have had a problem like that in the past. Are you using PLA and is it an all-metal hotend? If so, you could be retracting too far, thus getting rubbery PLA up in the higher part of the heatbreak...
Type: Posts; User: Alibert
I have had a problem like that in the past. Are you using PLA and is it an all-metal hotend? If so, you could be retracting too far, thus getting rubbery PLA up in the higher part of the heatbreak...