I haven't seen the episodes in question, but I'm sure I wouldn't let a small error like that bother me. I have been a big fan of New Tricks since it began, and am currently watching a re-run of the series on UKTV. There are a number of shows in which the actors leave or are replaced, take The Bill, for example, but I still watched it until the end. I will do the same with New Tricks.
Peter.