A user cannot delete a specific post in a channel on Teams, she has access to delete all other posts but not this specific one.
Does anyone else have the same problem in your organization?
As far as I know, team owner can have the capability to delete sent any messages if the setting is turned on in the messaging policy applied to the owner. Is this user you are talking abour the team owner and you've already turned on the "Owners can delete sent messages" setting in messaging policy? If this is not the case, I'd recommend enabling the setting via Teams admin center, wait for some time and then check if the owner of the team can delete this problematic post from the channel.
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