BBC have just started repeats of Francesco's Mediterranean Voyage, which I downloaded some time ago, using a simple search:
francesco_name_tv
fields name
fps25 0
subtitles 0
thumb 0
type tv
search0 francesco

I was surprised that get_iplayer is downloading the repeat alongside the old version, and I noticed that there is a subtle difference in filename, despite an identical PID
New:
Francescos_Mediterranean_Voyage_-_01._Arrivederci_Venezia_b00cjs85_editorial.mp4
Old:
Francescos_Mediterranean_Voyage_-_1._Arrivederci_Venezia_b00cjs85_original.mp4

I looked at the episode details where I can see (alongside lots of other stuff)
player https://www.bbc.co.uk/iplayer/episode/b00cjs85
fileprefix Francescos_Mediterranean_Voyage_-_01._Arrivederci_Venezia_b00cjs85_editorial

So it looks like get_iplayer doesn't rely on the PID alone, and does an exact filename match when detecting previous downloads. Would a matching PID not be enough?  Or do PIDs get re-used over time?
I think the editorial v original part of a filename might cause repetition problems for other users. The 01 versus 1 part of the filename might be easier to parse and ignore.
Not a big deal, but I'm making a mild suggestion that get_iplayer might simply match the PID rather than a full filename. Or might match Francescos_Mediterranean_Voyage_-_01._Arrivederci_Venezia, but with omission of the 0. After all, the web interface shows Episode Number 1, not 01.

[This behaviour is the same whether using the web interface or downloading from the command line]