The property SIMBAD ID (P3083) links to the database Simbad. The ID is composed with characters that can contain a + symbol.
In this case, the link to the database doesn't work, probably because the + symbol is being translated to "%2B" in the URL.
Example : Q13522, the ID is "beta+del", the expected link should be http://simbad.u-strasbg.fr/simbad/sim-id?Ident=beta+del, but instead, the link is http://simbad.u-strasbg.fr/simbad/sim-id?Ident=beta%2Bdel (error).
It looks to me these identifiers should not be entered with a plus, but rather with a space. While the web service supports pluses as far as I can see, it only uses them to encode spaces (http://simbad.u-strasbg.fr/simbad/sim-id?Ident=beta%20del also works and is also in line with the identifier on the page).
I suggest to decline this task, changing this will possible break other identifiers that actually contain a +. We can hardly support half-encoded identifiers as it's impossible to find out what has already been encoded how.