Not sure what state you are, but here your lease wouldn't be "void"  Anything that conflicts with the code would be (landlord-tenant code supersedes leases in DE anyway)I would just say you had them sign an older version of your lease in error and need them on the current one.

Ohio also has a couple of other special rules such as the CAT tax and a funky bonus depreciation treatment.

Most loan packages include something you sign that says that you will cooperate with them to correct any technical errors like this and I believe it also includes the ability for them to sign for you if you don't but obviously they prefer to have clean paperwork where you have signed it. 

Unless there is an obvious error, you will likely be fighting an uphill battle.  

Also see if you can pull up rental  and sold comps in the area using Zillow and Redfin and you have to give a   margin of error in their estimates and see if property appreciation is there for that area in case you are thinking of building equity.

If that is your primary focus it could convolute thinking and force unnecessary errors, in an already error prone business with a very high failure rate.

*Weaker than they were pretending it was.My apologies for such an embarrassing error 

They should write you a letter explaining the error and that they are going to charge you the additional $400 now.

95% of the issues with LVT/LVP installs are from user error. 

So it is alot of trial and error with people, and I can tell you that it is error more than not - that's my experience and I have been on the phone with vendors from at least 8 - 10 different markets all across the US in the last 2 years and some are good and knowledgeable and helpful and other you hang up wondering how the hell they make money doing what. they're doing.