Is it a persecution complex when many of these kinds of "technical errors" seem to so often befall people from one political persuasion? Some of them clearly weren't errors and that has happened enough that people stop believing that it's just an error, because these companies have demonstrated in the past that they don't mind doing moves such as that.

Yes. The fact that the OP had never heard of the National Union Party and jumped immediately to the conclusion that is was a 'euphemism sinister people use' rather than spend 30 seconds confirming that this was in fact the name of the party he represented as President at the time of his death is ample evidence of a persecution complex. Propensity to assume one's own ignorance of facts is evidence of malfeasance on the part of one's opponents is pretty much the definition of persecution complex.

I was being facetious; it appears it is your theory of mind which is lacking. Of course, this is no grave fault of yours. Noticing these subtle tricks takes special acuity. After a few dozen more Google queries and even examination of several different platforms entirely, the picture becomes much clearer.

> search results scrape Wikipedia and return the most recent party a politician belonged to?

Google for: "what party was Andrew Jackson in"

For me this shows "Democratic-Republican Party" - this was the first party he was part of - he was elected president while a member of the Democratic party and remained such until his death: https://en.wikipedia.org/wiki/Andrew_Jackson

So your theory does not hold.

Here we have someone who was a Republican being portrayed as something else and someone who was a Democrat being portrayed as something else - and in both cases there is political benefit to Democratic party in the US.