My final result: I returned the first MBP-13-TB with bad arrow keys and received a new one -- the new one was WORSE, not better; so I returned that too; got a full refund (thank you, Apple); and bought a new Macbook 12" which I have now received. It has the similar butterfly keyboard design, but, thankfully, this one works perfectly right out of the box. I'm still a little weary, as I've read that even this model has also seen some keyboard issues... but for now, at least I'm able to work without constant keyboard errors.
If anyone (or Apple) learns that this manufacturing/design flaw is finally fixed for the latest MB-Pro models, I will upgrade to that, as my work would benefit from the processing power... but for now, I'll take the compromise of a slightly slower machine for a keyboard that works.
Thanks to everyone writing here and to MacWorld for their recent article to help Apple be aware of this issue and (hopefully) to get it resolved for everyone.