Triple net lease/ selling business/ lease guarantee

I’m an owner of a small business in woodbury mn. I have a deal to sell the business after 4 yrs of good standing in the space. In order to get the lease I had to sign a lease guarantee which expires 2021. In order to get out of the lease I am told I need to find a new guarantor. I found a candidate that appears qualified (did a financial background check). But no response from the land lord after 4 months of repeated calls. This transfer is holding up the process as the owners won’t respond. Question: in minnesota, can the owners require a lease guarantor? Upon sale of a business, can the owners hold the original lease guarantor if a suitable transferee was found? Can anyone recommend a lawyer in Minn to advise me? ThankS.