Many Players Banned for Manual Trading Is Buy Low Sell High Against the Rules

Question about manual trading and bans

I have a question about manual trading in FC 27.

I’ve seen many people saying that they manually traded Silver players and were banned, even though they claim they used no external tools, bots, automation, or coin transfers.  For example, if I buy a player or consumable for 300 coins and later sell it for 2,000 because there is high demand for it, is this allowed?   I mean normal manual trading entirely within the game/app, with no external tools, no bots, no automation, and no transferring coins or items to a specific person.   I’m asking because I was unfortunately banned in FC 26 after doing similar trades. I also keep seeing other players in FC 27 saying they were banned after manually trading Silver players. I couldn’t find a clear rule stating that buying low and selling high is against the rules.

So can someone clarify: Is legitimate manual buy-low/sell-high trading actually allowed? If it is allowed, what exactly could trigger a ban when doing this?

I just want to understand the rules clearly so I don’t get banned again.