Underwriter wants proof of transfer of lease

[Kimber Lockhart]

I bought a Bay Area rent controlled fourplex earlier this year, and while working on a loan for a new purchase, the underwriter is refusing to consider the income for the fourplex without documentation of the transfer of the leases.  I don't think I have such documentation -- under rent control a new owner must assume the existing leases unless eviction criteria are met.  

I've provided documentation of annual rent increases and history of rent payments, apparently not to the underwriter's satisfaction.  Anyone faced this or have advice on what documentation I could try?

Thanks!