1: Where are you located
2: Who were you going to get to service it
What is actually wrong ?
Bubbles is at best a user problem and could be a slight change in Steam pressure or milk, that your not accounting for in your method?
That is, unless it has almost totally died ?
A: When did you last have it serviced
B: When did you last clean teh steam tip
C: What is the gauge reading before and during the process ?
D: How is teh temp of teh group / Coffee in teh cup ?
Group and Steam are related, so if teh steam was dead so to speak... Would expect to see / taste a difference in the shot as well ?
Ya steam valve/seat ;D