Sorry to say, but you've overlooked 1 critical part. If a unit is defective, it's not the 30-day return-policy that applies, but rather your right to a functioning unit as a paying customer. Your countrys laws for sales and commerce should apply in most cases, or in some cases with net-based sales, it's the laws of the country in which the company selling the unit is based.
A critical point is that it's the immediate seller that has the obligation towards you. So if you bought it at a local store, they should be your first point of attack. What they in turn have of relations to their supplier is none of your concern, eventhough many stores will try to use it as an excuse to slack on service.
Beyond that, most manufacturers will usually supply their own waranty agreement, usually based on the law of the country in which they're based. So if your local waranty is expired, in some cases the manufacturer will be supplying a longer waranty, in which case you must deal with the manufacturer directly.
To my knowledge in all of EU atleast, you have 2 years from purchase/receiving of the unit, in which time the seller are obliged to take the unit back and fix the problem or give you a full refund. And i believe it's not much different in the US, Canada etc. Not sure about the far east though.
In my neck of the woods, within the first 6 months the problem are automaticly assumed to be an pre-existing issue, and seller have the burden of proof if he wants to argue you to be the cause of the problem (like if you smashed it or poured water into it). So mostly it's just exchanged right then and there, if there's no visible evidence of mistreatment.
After 6 months, the burden of proof falls on buyer (you), where you have to argue for the problem not being of your doing. I've never found the latter to be an issue. And atleast in my experience only few shops are big enough bastards to make any trouble.
So quite frankly you shot yourself in the foot by selling it on instead of returning it to where you bought it. If you gave the guy you sold it to all the proper documentation, he may very well just have returned it to the store afterwards and gotten it fixed or replaced with a brand new unit.
For the rest of it, i've heard alot of horror stories about Arturia, and have honestly come to doubt what to believe.
My own MiniBrute have run flawlessly for almost a year now, so i can't really say how their service is, as i've never needed it.
From a practical standpoint, you're not completely stuck in your current position. You can actually ask the seller to help you fix the problem with your MiniLab, again they are actually obliged. And eventhough you've registered the software, Arturia can unregister it for you, in which case it should be eligible to return for a full refund.
So i'd do what everybody else does: Attempt to annoy either the store where you bought your Minilab, or Arturia themselves, and see what comes of it. Worst case scenario, you wait for a fix. The AnalogLab software is quite new, and while it's at best questionable that they send out a software which is apparently so buggy, it's likely future versions will provide major improvements to stability and overall functionality. But i fully understand the wait is painful.