It has a more difficult time, as it was designed before SSD's were prevalent. Not impossible to use SSD's with the 1680 series, but it will have additional caveats, even with the newer settings made available in the firmware as it doesn't have the additional hardware support that's in the newer LSI chips used in the 188x series.
Firmware incompatibilities as I expected. At least they will work, even if not with the settings you'd hoped to use, unlike the Kingstons you mention.
Unfortunately, this will continue to be a problem over time (even happens with mechanical disks, so it's not solely an issue with SSD's). Which is why checking the HDD Compatibility List can really be worthwhile (will indicate limitations if it's not 100% functional, such as a reduced setting or need to disable a feature, such as NCQ).
At least you've got them running. 🙂