A preset won't export no matter what install of FH it's in, no matter what slot it's in. I also have a crash looming in Preset slot 2 of one install when that slot is unmodified.
That troublesome preset's slot is 1, but I put it in slot 3 to test, still didn't work.
I didn't keep track of any changes in the preset's size, it is 13.6 MB unexported.
I don't think the preset has exported successfully before on either install.