It very well could be, I'm positive I would have run into this issue before.
I have no idea if this information is helpful at all, but I'm on running Spriter 4.1 from Steam on a Windows 7 PC, and the last time I used it was 10/8 (where i had no problems) Hope that helps.
-EDIT- Just to be absolutely sure, I did some extra tests with the project i was having trouble with. it turns out it was a more specific problem than I thought:
This bug occurs when there are only 2 keyframes in animation, and repeat playback is turned off.
Translating a bone in the second frame will overwrite the first frame's scale and rotation to be that of the second frame's.