CAEmitterLayer with multiple emitterCells no longer loops in iOS12

Has anyone noticed this? I have a number of particle effects in a working, shipping app that have ceased to work under iOS12. The problem is not only looping while the animation is playing, but even if i slowly, manually set the time back to 0, the particles disappear. and never reappear. One effect had 2 CAEmitterCells in the emitterlayer's emitterCells array. When I built the same code on an iOS11 iPad and an iPad with iOS12.0.1, the problem appeared only on the iOS 12 device. Removing one of the cells from that array, so it only had a single cell fixed the issue. I have fireworks that use multiple cells, as they must, which no longer work on iOS 12.


Help?

Replies

I neglected an apparently critical detail, which is that the particles are running a layer in an AVComposition.