When Phryne sneaks onto the ship via the rope ladder, one can see a simple set of metal stairs with a white metal hand rail on deck to her right; but, when she gets aboard, the stairs aren't there and have been replaced by a pile of ropes, boxes and burlap sacks.
When Phryne uses Jack's necktie to show him a particular type of knot, one angle shows the collar of his shirt open, another shows it buttoned all the way up.
While Phryne listens in on Sanderson and Jack's conversation she is standing just outside the glass on the office door with her shadow visible from the inside. In two shots before she walks away, however, the shadow is not seen from the inside.
Miss Fisher's kitchen calendar shows June with the 1st on a Tuesday. In 1929, when this story takes place, June 1st falls on a Saturday. The nearest years with the 1st of June falling on a Tuesday are 1926 and 1937.
The murdered girl, Bernadette, was named after Saint Bernadette Soubirous. The episode is set in the 1920's and the victim's age was about 14 or 15 at that time, so she was born around 1910's, and the nuns named her after the saint. Bernadette Soubirous was not canonized (declared a saint) by the Catholic Church until December 8, 1933.
The long black car is an V16 Cadillac, only two of which were known to have been built as right-hand drive, as for export to Commonwealth markets. A RHD V12 Cadillac before about 1935 would be an EXTREMELY (almost impossible to believe) likelihood.