Huh. This is really weird. I see the same. When I have Center->X = 0.6 in the Duplicate node, all the copies disappear.
A simple workaround is to use a slightly difference value for Center->X, like 0.60001. It also works when changing any other value, like Size or Angle or Y.
It also happens with Center->Y = 0.6, or either of them at 0.7, 0.8, 0.9. Likewise 0.65, 0.75. it seems any multiple of 0.05.
At first I thought maybe there was a logical explanation for this. But what's even weirder is the problem is fixed by manipulating
any other control, including Blend, Burn In, Subtractive/Additive. The smallest tweak to any of those controls will cause all the copies to appear as expected!
So it sure feels like a bug? Unless there's some weird interaction going on here I can't figure out? Hopefully an expert will chip in and confirm

PS. I tested in Fusion Studio 16.2.4, so if an issue exists it's common to both Resolve and Fusion Studio.