Section 8 tenant refuses to sign rent increase form

Our family owns a home occupied by a section 8 tenant.  The last time the rent was increased was more than 3 years ago. The tenant is currently paying less than current market rate, and we are only asking for an increase of 6%.  This tenant has been a pain in the *** and high maintenance from the get go, but we are stuck with them.  In order to receive a rent increase, the rent increase request form submitted to the Housing Authority must be signed by the tenant and landlord. Our section 8 tenant is refusing to sign this form.  Has anyone ever dealt with a situation like this?

BTW, this is in the SF Bay Area in a rent controlled and tenant friendly city so it's next to impossible to evict.