In the Footsteps of a Killer - S6-E7
Factual error: In the denouement, DI Jack Mooney says that all the suspects could prove they were not in the building on Thursday June 22 2009. Which was a Monday. (00:41:10)
Factual error: Emer Byrne's Irish passport is fake. Look at the expiration date; the day of that date does not match the date of issue. A passport issued on September 24 wouldn't expire on September 01 as seen there, but on September 23. (00:16:15)
Factual error: When Humphrey makes the big reveal opening the suitcase full of cash, it's a bunch of wad of bills, each with the currency straps indicating a value of 50,000 (Eastern Caribbean) dollars. Thing is, it's all in $50 notes, which means there should be 1,000 bills in each wad, which is obviously not the case. (00:47:20)
Answer: There's probably no particular reason. Sets and props on long-running TV shows often change as needed and for various reasons throughout a series run.
raywest ★
As long as such changes aren't an obvious continuity mistake (e.g. changing multiple times during a day), one can just assume the change happened in-universe as well. Things do get broken or updated occasionally. It adds a bit of realism, in my opinion.