Hi Ben,
I also tried to recreate this in RedShift, U-Render and ProRender it works fine. Corona interactive is the only one giving faulty feedback, so it might be Corona after all.
Those others are GPU renderers, so not a fair test, really. The only thing I can think of is that I'm using dual CPUs in both workstations. Maybe you're using a single socket?
W1: 2x E2670, 64GB DDR3
W2: 2x E2695 v4, 256 DDR4
@burnin
I don't know, since I don't have any CPU interactive renderers. Maybe arnold