I had the setting for the number of rows of signals set to 10. During the last update, this got reset to 2, deleting a ton of my requests.

Oh, bummer. So they have a facility in migrations that is for settings and I used that. However, after reading your post here I wen't to see what was up and ran across this.

https://forums.factorio.com/viewtopic.php?t=76036

Apparently settings don't migrate :/ I'm truly sorry about this. I don't really see a good way back either. If you've saved since then, you'll have to re-setup those requests. If you still have the pre-migration save, you can change the setting and load it up. The requests should still be there.

I think it's a slightly deeper problem than that. I think that, through the migration, NONE of the output signals of any of the combinators should've changed without warning the player that something changed and that they might not want to overwrite the save. A similar problem occurred with the output of some of my combinator stations where, before the update, the combinator output was as intended, but after the update, some checkboxes got checked/unchecked and the combinator output changed, making the station not work correctly.

I completely agree. None of your signals were supposed to be lost. I thought I tested all the scenarios thouroughly, alas I missed a pretty big one. For that I am truely sorry. I never intended to complicate anyone's game. The setting that didn't migrate only related to loosing request signals in rows above 2. Yes, there was a differen bug that also caused some reqeust thresholds to get out of sorts. It is alos fixed.

Again, I wish I could go back in time and fix these things before it impacted anyones factories. Rest assured, I am working them through and will likely have a release this weekend with fixes.