Every lease of all lands, wharves, docks, and real and personal property of a port district for a term of more than one year shall have the rent secured by rental insurance, bond, or other security satisfactory to the port commission, in an amount equal to one-sixth the total rent, but in no case shall such security be less than an amount equal to one year's rent or more than an amount equal to three years' rent. Evidence of the existence of such insurance, bonds, or security shall be on file with the commission at all times during the term of the lease: PROVIDED, That nothing in this section shall prevent the port commission from requiring additional security on leases or provisions thereof, or on other agreements to use port facilities: PROVIDED FURTHER, That any security agreement may provide for termination on the anniversary date of such agreement on not less than one year's written notice to the port if said lease is not in default at the time of said notice: PROVIDED FURTHER, That if the security as required herein is not maintained throughout the full term of the lease, said lease shall be considered in default: PROVIDED, HOWEVER, That the port commission may in its discretion waive the rent security requirement or lower the amount of such requirement on the lease of real and/or personal port property.