I have yet to see this in any other mode that I have played so for me it just seems to be an issue with Pro Clubs. The offside rule is that age old eye rolling law that every non footballer asks about, and men feel manly while they think they are expertly explaining it. As you have clicked on this article I can only assume you're a FIFA and football fan so I don't feel I should have to explain what offside is, but since I'm nice, here is a Wikipedia link that explains everything. In Pro Clubs if the opposing team maniacally brings their goalkeeper out, but still has a defender(s) behind him. If you pass the ball to one of your players behind the goalkeeper and you are in the opposing teams half, then for some ludicrous reason you are called for offside. This has cropped up time and time again online for my team and leads to many annoying moments where a simple tap in is denied. I'm fooled by it every time which subsequently leads to annoyance once I realised what has happened. I'm not sure if anyone else has noticed this, but if you have please comment below but it has happened to my club on numerous occasions so I doubt it is a one team focused glitch, and something that should be improved upon so my team can claim more victories!