I kept trying to get around this, and do have a solution. It is inelegant, but does work:

– Insert breaks at the beginning of the paragraphs you want.

– Place a small text box somewhere outside the page (maybe near the beginning of the next frame). Make them 1-2 em thin but longish.

– Thread your text into the dummy box first, then into the next frame you really want it in.

If there's plenty of space at the bottom of the first frame, you don't really need the box, and everything works normally.

If you're right on the edge of using up the first frame, that break character will flow into the dummy box, but the next (real) paragraph won't fit, so will flow into your second proper frame.

Kind of a pain since you have to do it for every frame, but I haven't found any other solution.

I've just run across this as well, and spent some time investigating.

It is not a justification issue: it relates to the way paragraphs and characters work. Because a break is actually a character, InDesign requires is be located inside a paragraph. The actual break is created *after* the break character.

These two facts create the problem: the break character will be placed at the end of a paragraph — the last in one frame — but that paragraph will span the break and flow into a new frame. After the paragraph concludes, an “end of paragraph” symbol is (automatically) placed, which renders as a line break — plus any after-paragraph spacing will take effect. That means there's going to be a gap at the beginning of the new frame.

So basically, InDesign assumes you're using frame breaks inside of paragraphs, and want them that way. When in fact, we don't; we want them between paragraphs. I haven't come up with any good solution so far.