It isn't two suffixes - 'sabre of swiftness' is a base item. Of course, it should probably not be able to have suffixes generated.

Oh, ok. I thought "of swiftness" was a regular suffix. So apparently the sabre is a naturally suffixed item like halberd of defense or sword of sharpness.
In that case it's the same problem as in issue 2754, where one of the new artifacts had a suffix. That was fixed, but only for that artifact (rapier of the needle).

This might be the case for all the newly added weapons then.

spiked maul of devastation "Foeslammer" of devastation :)

Fixed for "sabre of swiftness", the item definition for "maul of devastation" is fine.