Span columns not working properly in 15.0

I recently updated to the most recent InDesign and now am finding that I have very little control over the text under a spanned column headline. ID will bump the 2 column text to the next page even though the spanned column headline is only halfway down the first page, and I can't get the text to come back under its heading where it should be, nor can I identify why it's doing this. Also the split column text is not flowing into two columns beneath spanned headings. It flows in the column on the left, but the right hand column is empty. Previously, if I set a heading to span columns, it would make 2 column text above it flow neatly into two columns, as one would expect. Help! Very frustrating!