Throw out every line of code in VPX13 and start again.
VPX12 is excellent. Stable. Usable. Saleable.
VPX13 is none of those things.
It is not too late to correct this. I have 25+ years of experience (at all levels) in the commercial software industry. This is my assessment and recommendation based on my knowledge of your product and my experience of how it’s built, maintained and marketed.
You need some brutal truth here. Please try to see beyond the criticisms and instead, focus on this chance to turn it around.
You have released a product, VPX13, that is not fit for purpose. It is actually the worst product I have seen released in the commercial market for over two decades. It barely qualifies as an Alpha release.
Whether you are aware of it nor not, you now have an unstable (and now unmaintainable) code base. So every minute and every dollar you spend trying to fix VPX13 is bleeding out resources. Looking ahead, this also removes any possible path to eventually get you to VPX14.
Your current testing regime is a complete failure. I can only assume that you have no code testing, no code peer review and no automated testing. Which is terrifying.
1. Rollback all VPX13 code changes. Go into your Version Control software and rollback every last line of code that was changed since the last VPX12 patch.
2. Issue a Mia Culpa statement and refunds to recent purchasers of VPX13.
3. Implement a competent testing regime. Outsource it if necessary. Do you have automated testing? It’s never too late to implement it.
4. Your personnel who certified that VPX13 was ‘release ready’ did it for a reason. Find out what that reason was. And stop it from happening again in the future.
5. There are multiple people responsible for the failure of VPX13. At the very least, the Project Manager would be sacked by the end of the business day if this was my business. They have failed at their job.
As for the other parties, they’ll either learn from this, or continue along unchanged, until your company folds.
Unstable code will kill a software business. That's not an opinion.