autobuild happily accepts multiple declarations of the same 3P.

[Nicky-D]

For example here I did catch a double of meshoptimizer (linux64). I suppose those come through merges and autobuild then latter happily accepts such a file. Either pulling the first or last.
Here is another one I found today Nicky-D/viewer@043a13b

autobuild should at least warn if there is multiple (conflicting) definitions of one 3P

[nat-goodspeed]

Seems like this would be a fix in python-llsd deserialization: detecting duplicate serialized map keys. By the time autobuild sees the data, there are no duplicate keys because one of them has already overwritten the other.