In the final "aftermath" dinner scene, the wall behind Paul Drake in his close-up shots looks very different from what is seen of the restaurant background in the shots of the whole group at the table, as well as in the other actors' close-ups. The audio on William Hopper's voice also sounds slightly different in the close-up shots, compared to when he speaks in the group shots. His close-ups clearly were done at a different time on a different set.
The scenes on stage show the actors performing with an orchestra pit. But the play is Romeo & Juliet, which isn't a musical.
When Perry asks Paul about the shipment of costumes from South Africa, Paul does NOT reply "the customs boys have been asking questions about those customs". He does not say "customs" twice. He did pronounce "costumes" at the end of the sentence.
It's very difficult to believe that Amos Martin could not recognize Perry Mason until he took off his sunglasses. It was daylight. If the glasses were so dark he couldn't recognize Perry Mason in the daylight, he wouldn't be able to see where he was walking.
Prop swords are not sharp for obvious reasons and are useless for murder weapons.