It may be an example of "crosstalk", where rigging information in the clothing item is affecting the rig of the figure that it conforms to.  In old versions of Poser, prior to Poser 5, this was a common problem that was also exploited for practical use.  I had understood that this was changed heavily in Poser 5 and later so that it was less likely to happen by accident, but you seem to have found some items that have crosstalk problems.  Best to contact the clothing vendor, that may actually be semi-intended behavior (or if not, the vendor probably ought to correct the problem).
edit - how to narrow down which one, well, conform one item and run a variety of poses, repeat until you hit the problem item.

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