The 6s rigs are common to all have some play in the bellcrank posts, up & down. Bearings can be swapped for the bronze bushings, it helps, & adding shims(6×8) on top of them, under the top plate, to eliminate all up & down play. The other area that has play, is the ackerman plate. It can move up & down on the step pins that attach it to the bellcrank arms. That's a little tougher to eliminate as stock, can't just tighten the step pins, they'll snap. A shim can be added there, but normally just left as is, unless going to an aftermarket setup. As
@Chapinb stated, check the pillow balls for play. Also some play is in the steering rod ends on the pivot balls & that’s normal. Also check the servo link, if its worn. Adding a HD adjustable aluminum servo saver is a great upgrade also over the composite one.