Hi Robyn,

A bread machine cookbook I borrowed from the library had the following baking tip:

Breads can collapse of they're too large for the pan, if there is too much yeast, or if salt is omitted. Also check the consistence of the bread as the dough kneads (dough should form a ball that holds together); it may need a little more flour. If the weather is warm and humid, the dough may rise too fast, then collapse before baking begins; use the rapid cycle.

Hope this helps!
Susan, Hawaii