Formula.Firewall: Query references other queries, so it may not directly access a data source.

I am trying to figure out why this is receiving the the Formula.Firewall error. Can anyone please tell me what is causing the error?

let
    Source = Passing,
    #"Removed Other Columns" = Table.SelectColumns(Source,{"Season", "PlayerName", "PlayerShortName", "PlayerLastName", "Team", "SeasonPlayerTeamKey"}),
    #"Invoked Custom Function" = Table.AddColumn(#"Removed Other Columns", "fxGetQBProfiles", each fxGetQBProfiles([Season], [PlayerName])),
    #"Expanded fxGetQBProfiles" = Table.ExpandTableColumn(#"Invoked Custom Function", "fxGetQBProfiles", {"PlayerURL", "Position", "PlayerImgURL"}, {"PlayerURL", "Position", "PlayerImgURL"})
in
    #"Expanded fxGetQBProfiles"