Episode #4.1 - S4-E1
Continuity mistake: Lucy Thomson sits at a table outside while her brother Daniel is dealing with distillery paperwork. She puts her cell phone next to her. When it rings a few shots later, the phone is at the corner of that table. (00:15:45)
Episode #4.7 - S4-E7
Other mistake: Spoiler: While unmasking the culprit, Goodman never explains what happened to the real Dominic Claydon. Only that the perpetrator used his identity to get what he wanted.
Other mistake: Joséphine Jobert is a Sergeant (the commissioner introduces her as such at the end of the first episode), but in the end credits of all the episodes before she takes over for Camille Bordey and becomes officially a Detective Sergeant, she is merely credited as "Officer Florence Cassell." By comparison, Fidel was credited as "Sergeant Fidel Best", even not being a DS.
Episode #4.6 - S4-E6
Revealing mistake: Florence passes a mug of coffee to her boss, who goes on to sit in his chair and have a tragic overacting accident. However, when things were still normal and he merely approached the desk, you could see Florence already stop drinking and frown preoccupied before anything bad happened. (00:06:10)
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.