Yes, twin fin caused tail flutter and 1st prototype crashed because of this!
Tail unit was completely redesigned.
Ju-87V1 was powered by a 640 hp R.R. Kestrel engine driving a two-bladed propeller and it was fitted witout the later wing dive brakes.
(info: W. Green, Famous bombers of the Second World War 1st volume, Macdonald 1959)