I don't see the need for shims except that a person does not have the tools to make a correction. You need to take the metal bonnet off and locate the reel table mount screws and position the reel table above the face so that the tape feeds directly down the middle and packs the tape in the center of the hub. This is not a highly technical adjustment just some aggravation. You might also have a bent tension arm due to some movement or dropping an item on the deck. It is not common for the reel table to change position by itself but mostly from bad shipping. You will need a long Hex metric bit. I use excellite tools for this.
Who am I to tell you this? I am an ex- Lead Technician from Teac Chicago Factory Service still doing repairs in the Chicago area. I work on these decks 12 hours a day even now.