I have been making jewlery pendants for years, but recently random batches, in random spots on the firing plate/brick I will have pieces where the top clear layer has slid forward/off the piecea about 1/2 way. I can’t find a common denominator, it happens with tested glass, it happens with non-tested glass; it happens in different spots in the kiln, and in the same batch other pieces will have fused/fired just fine. It also happens on pieces I tack glue, and on pieces I don’t tack glue. The only change I have done is I started using the thinner system 96 clear at the toppers about a year ago. I also tried leveling the kiln, thinking maybe that was the problem. Has anyone ever had similar experiences that they can share their insight with me? Out of the last 10 firings, I have had 4 firing brick batches with this issue.