my bread machine keep crashing top of loaves when baking help?

i got a sunbeam 5890 all bread loaves crashed on the top when baking–(I have baked bread by hand for 30 years)- called sunbeam they replaced it 3 times– & now replaced it with a oster – bread is still crashing when baking–i tried different yeasts- flours- recipes-all flop on the top causing a dense heavy bread—at my wits end-WHAT IS CAUSING THIS–never had these problems in Illinois
~gone goofy in AZ!!