Statue 102.141(7)(c):
The canvassing board shall submit on forms or in formats provided by the division a second set of unofficial returns to the Department of State for each federal, statewide, state, or multicounty office or ballot measure. The returns shall be filed no later than 3 p.m. on the 5th day after any primary election and no later than 3 p.m. on the 9th day after any general election in which a recount was ordered by the Secretary of State. If the canvassing board is unable to complete the recount prescribed in this subsection by the deadline, the second set of unofficial returns submitted by the canvassing board shall be identical to the initial unofficial returns and the submission shall also include a detailed explanation of why it was unable to timely complete the recount. However, the canvassing board shall complete the recount prescribed in this subsection, along with any manual recount prescribed in s. 102.166, and certify election returns in accordance with the requirements of this chapter.
I don't know how to read the legislative history to see when this was changed. It might have been pursuant to the mess in Nov. 2000. It might be what SCOTUS was referring to as the deadline for providing a "safe harbor". Dunno.
Don't know why there were so few machines pressed into service for this. But they might make the deadline, you never know.
Or maybe somebody will simply declare it an emergency. After all, anything that makes anybody miss a deadline is an emergency to the person who stands to benefit from extending the deadline.