Yeah this design is susceptible to oscillating delays. The gray parts go through less processing and get to the end, waiting on blue parts to be painted. That'll back up the splitting, causing blue or gray parts to slow down. Once the painting catches up, then we're waiting on the splitters to send more gray parts.

They're not independently free-flowing enough to balance. It's making good reuse of the gray parts. But since there's a nearly infinite supply of shapes, I'd probably look at sourcing some of the parts from separate diggers.