Episode #3.7 - S3-E7
Revealing mistake: Dwayne aided by Emily is bringing in the two boxes of papers from the storage. Transporting them is a difficult task with the storm that is raging on. A strange storm that happens to shake the plants in the foreground, but with Caroline Proust's hair and the leaves of the trees on the other side completely untouched. (00:16:40)
Episode #3.1 - S3-E1
Revealing mistake: When Goodman looks at the two old pictures from the graduation ceremony side by side, they are blatantly photoshopped in a poor way; look at the way the characters stand out from the background, the light on the man on the right of the left pic, and there's even a frock or bag that two of the women carry that is a copy/paste from one picture to the other. (00:39:10)
Episode #2.5 - S2-E5
Revealing mistake: When Ben Miller asks for the forensics report on the oyster and shot glass, the report has egregious spelling mistakes ("Specimin" instead of Specimen) and shows the victim testing positive for Oxycodone rather than strychnine! For the record, it is an entirely different lab test (a real one, with 'specimen' spelt correctly) done for a patient under prescription medications (morphine, oxycodone and benadryl) and its date is inconsistent with every other episode (it's a 03/19/2010 document and in the first season it was established the year was 2011), but these last details can be noticed only if you freeze-frame. (00:42:00)
Episode #2.1 - S2-E1
Revealing mistake: Richard at home is reading a book on slavery. An English book, at least the cover and the big header of the first internal page are in English, and about slavery. But a quick peek before the cut easily reveals that the book is written in French and talks about cocktails. (00:28:10)
Episode #2.7 - S2-E7
Revealing mistake: When we see the killer deal the fatal strike, the pipe misses a mile to the left. (00:48:00)
Revealing mistake: Jack searches for Bryn Williams. We see the page with the results. Florence suggests him then to change to William Bryn, he types it, but the next close-up shows the results page with the query unchanged from before. Still, the bottom result (the top one are still all "Bryn Williams) is the one ("William Bryn") they are looking for. (00:16:20)
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.