I'm going nuts here. I've tried both 2014 and 2015 ID now. They both behave the same. Here's a simple column of text in a two-column text box. I want ALL of the text to still be in the left column, because, . . . , that's where it belongs. Until there's more text that is. But, here, not even halfway down the left column and the text jumps over to the second column, aligning vertically, perfectly, with the first paragraph of the left column. There's still like 4 inches of space left in the left column.
There's no baseline grid active. The text box is set to top align, not vertically justify. Balance columns is not checked.
It's just 9/10 Warnock, with 3 pts. above each para.
Things like this make me feel old and in the way. ( -: Maybe there's something obvious here.
Never mind!! Duh. Yes, I had a paragraph style way down in there that was spanning columns.
Not sure this will help, but I've had similar weirdness before and it involved the Keep Options in the paragraph settings. . . . Had a Word file that brought in settings that required lines being kept together. . . .
Sorry I don't have the definite answer. . . . I'm old too, so I feel your pain.
Thanks, April. Yeh, I figured it out. I had a "spanning column" entry in one of the paragraph styles down there. That'll do it.