Factual error: The "whaling boat" is too small to function as such. It isn't large enough to hold a fin, let alone disassemble a humpback whale.
Factual error: Right before Frank humiliates Dorothy for the first time, he blows out one of the gaslights in her apartment. That is never done in real life, for the same reason you would not blow out the pilot in your stove.
Factual error: When Mitchell is working on his Jaguar, he walks from the bench to the car, places a spark plug, then tightens it with a ratchet wrench. The audio proves, however, that the wrench is set to loosen the plug, not tighten it. (01:11:50)
Factual error: Apparently, Ratigan had to cross the River Thames to reach Big Ben from Buckingham Palace as evidenced by him tossing Fidget into the river before taking reign of the blimp. However, the two landmarks are on the same side of the river.
Suggested correction: Ratigan changed direction multiple times during the chase because he was trying to get away from Basil. He may have flown away from that side of the river, but then after changing direction he flew across to the side he came from again.