What you should do is highly dependant on your situation with the OEM. If you modify the code your warranty is VOID, doesn't matter if your modifications have anything to do with what happens, if you change the code it is void.
Call the company and ask for the password, tell them that you aren't interested in stealing their proprietary technolgy and making your own sealers, just simply want to make some changes to the way that YOUR machine operates. It will hurt your pride but it may be benefical to ask them to make the changes for you. Swallow it, the company you work for wants a working machine and if that is the best way to deliver it to them then so be it.
I spent some time looking at the products from the company you are dealing with, from a controls standpoint it doesn't look like rocket science (despite their marketing claims). If they wan't to be silly, reverse engineer what they did and do it yourself and never spend any money with them again!
I don't have a problem holding machine suppliers accountable for their claims, just be reasonable.
I once had a very good machine supplier for me go bankrupt. They bit off a 10M dollar job and quoted performance spec's for about 300 products. They achieved 100% performance for 95% of the products. They could only achieve 90% performance for the other 5% of product. The customer witheld their 10% hold back because the contract spec's were not met. The machine company wen't broke because of it. Assanine, who wins?