Resize handles disappear when object is still pretty large (Windows only)
When an object is very small on screen -- either due to zooming out, or just because it's small -- XD hides some resize handles to prevent them from jumbling all together.
On Mac, handles don't disappear until they're really overlapping. At 100% zoom, you can make a square as small as 16x16 and still see all eight handles (and it'll still give you four handles all the way down to 8x8).
On Windows however, you can only go down to 64x64 before handles start vanishing. And it'll drop from 4 handles to 1 at any size below 32x32.
This makes sense when you're using a touchscreen device (fingers are not very precise!), but if you have a mouse plugged in XD on Windows should use the same size thresholds as on Mac.
You should see an improvement on this behavior on Windows in the August release of XD. Please check it out and let us know what you think!