A cheap replacement wheel, noticed the cluster moving ?2mm? side to side spinning.
If the wheel is spinning fast the imballance is felt in the frame.

Bent axle? Or possibly the freehub body is as well bent?

Anyway...the rim is Mavic, true and spokes fine. Is a STX worth the price of a new axle and shop fee?
I've no idea where it falls in Shimanos line -garbage or not?
This a 2'nd wheel to use while a beefier one is built..I'm unsure if I should put money into it.
I'm fine with the rim....
I'm thinking about cutting out the body and re-lacing better than repairing the STX.

Any suggestions?

A wobble necessarily doesn't mean your freehub's gone bad. Most all freehubs have some visible wobble to some degree. Both (two wheelsets) my XT hubs/cassettes wobble when free-wheeling.

The first time I noticed this on my Coda hubs and XT cassette, I couldn't believe it. Apparently though, like the fixer said, a certain amount of wobble is normal for certain hubs.

Why would the 'flex' be transfered into the frame when the cluster is stopped and the wheel spinning?
It's internal, the cluster wobble is a result of axle or freewheel imballance.
Thanks for replies..
I'm thinking now that the freewheel body fixing bolt may be bent or not tightened down..

.........I have no clue, oh well...lbs time...again.

All freewheels and freehubs have a slight wobble while coasting.

The wobble is because there is a small amount of spacing in the bearings to allow them to rotate freely. As that space articulates (great word, no?) around the axle the freehub/cluster shifts position slightly.

As long as it does not affect your shifting it is not a problem.

Don't obsess...