Oh, I'm curious if anyone knows more. I've had this happen too, with commercially available fonts, in CS4 (only the squooshed justified line, where the red arrow is, though; not the other blobs); I've been able to fix it locally by changing the hyphenation somewhere before or after the line in question. But I wonder why it happens – I've been thinking it's probably InDesign getting confused about H&Js (I've only had it happen in longer documents / books).

> I've been able to fix it locally by changing the hyphenation somewhere before or after the line in question.

I’ve had this sort of thing occur if I limit the number of hyphens in a row too severely. A line that obviously begs for hyphenation doesn’t have any — and I can’t seem to force it to — until I realize that it has reached its limit and that’s why it’s squooshing or spacing in an extreme fashion.

Another example of why it’s not necessarily good to tie the hands of InD’s H&J engine too tightly.

I don’t think that’s what’s going on in the OP’s example. And it might not be what’s going on in your case.

But I thought I’d mention it, since it’s easy to overlook.

Thanks all.
I had a feeling it had something to do with the ligatures. When the ligatures are turned off in INDD, the problem is solved.

Nevertheless, could it be there's some bad coding in the .otf? I did design some ligatures and stylistic alternates, but removed them in a later stage. Could it be that the code for these is still in the .otf file and corrupting it?

Problem solved! There was some obsolete coding left.

Thanks for your help!