Further to the Florida race for U.S. Senator. Reports in the news media point to the low count of votes in Broward County for the U.S. Senate race (~682,000 - all candidates) compared with the Governor's race (~707,000) and even the Florida Attorney General's race (~696,000). Undercounted ballots, maybe, that need a hand count? (Broward Co. is one of the more populous and Democratic-leaning counties among the 67 counties in Florida.)
My from-a-distance analysis, alas, says, "No. It is a ballot problem." Remembering how the Palm Beach County ballots in the year 2000 were difficult to read and caused that election for U.S. President to go the way it did, I had a look at a Broward County ballot. I note that the ballot instructions are in the first column (of the multi-columned ballot) along with the two federal office races (U.S. Senate and U.S. House of Representatives). The second column has the Governor's race at the top, followed by other state races, etc. It would be easy for someone to skip the instructions and not notice the two federal office races. After completing the five-paged ballot (!), a voter might not realize they never saw the federal office races. In contrast, my Leon County ballot (also a multi-column ballot that is read by an optical scanner, but only 2 pages long, and fewer columns per page) had the instructions in a banner that was above all page 1 columns - not possible to miss the first column of races.
Screen print from the upper left corner of two ballots (reduced in size, too) - Broward Co. and Leon Co.: