I've seen the same with Hebrew. It's not nearly as widely spoken as Arabic but graphic artists like to include it on their designs and so on because of the unique letters which really contrast to the Latin alphabet.

Mistakes include: 1) Left to right letters 2) Bad translations, especially dating to the days when Google translate was not as good. 3) Incorrect grammar e.g. singular instead of plural, masculine words mixed with feminine. "Welcome" should be plural unless you really only want to welcome one person! 4) Spelling typos