It appears the issue with adding 1 to 2 Kg's for USA Tracked parcels HAS been resolved. Have updated 3 items with no error messages and the applicable rate displays as it should.
I am so glad to hear this @lotzofuniquegoodies ! I haven't gotten an update from tech on this one yet, so I'm wondering if I'll get a mystery email from them later today with 'oh that's taken care of'.