Just tried the same in VFP 9.0 -- problem does not occur in that version. So it appears to be limited to VFP 6.0 (don't have the VFP versions between 6.0 and 9.0 -- so I can't confirm if this is strictly in 6.0 only)

tried a few more things in VFP 6.0
* Problem does not occur with spinner within a container on form
* problem occurs with spinner in container on page
* creating subclass of spinner and placing that subclass on page of pageframe still results in the problem