Kiln shelf bubbles

[lhvhstudio]

Help! 4 th full bubble squeeze firing that has resulted in shelf to glass large bubbles. I have scrapped and cleaned my kiln shelves, re applied kiln wash, pre-dryed them at 500 for 20 minutes, re entered all my kiln schedules to full fuse bubble squeeze for the size of the project. Non of the bubbled pieces had glass or metal inclusions. Simple 6mm set up. Only diff is I’m now using bullseye kiln wash and have changed to the recommended 5 wash pattern from a 3 wash I’ve done for the past 20 years. I’m so bummed - I can’t think of anything else that would cause this... input please from wiser artists