Its not with teams so much as it is EP's or Head Judges or someone of that 'power'
Ive done judging for several smaller events and a few National. The stories that the judges around me tell are horrendous, and yes, I have experienced it first hand as a judge myself, so its not hearsay.
In my experience, the EP let me know that he changed my score so that team A could win because they brought a lot of teams to the event. Ive also had numerous judges 'threaten' to judge me and my programs poorly due to personal differences outside of cheer. As much as I have heard and seen it, I can only imagine how much it truly happens.