Does write node tie to cache?
Working with 2.3.11Release, A lot of time, if I zoom in and out, viewport will not refresh correctly, it will have blocks of black after zoom out, and it will actually render like this. Also, If rendered with viewport zoom-in, seeing only part of frame, it sometimes just render that part of frame with stretch pixels outside of that zoomed-in area. Try clear all cache, sometimes it works, sometimes it does not.
This may also be due to bugs or errors in the plugins. The cache system was completely reworked for Natron 3.0, but unfortunately was never stable enough to be considered ready for release. Caching is a very complicated issue.
Is there any older version that has much more stable RotoPaint and cache? I spent 1 hour yesterday trying to just render out 28 frames without RotoPaint node flicking and cache side effects. RotoPaint node sometimes require manually turning lifetime back and forth to get it work again.
What OS are you using? Natron on Linux has the reputation to be more stable.
Hint: if you rotopaint over the result of a compositing graph, then use the disk cache node to cache to disk everything above rotopaint. This make things a lot easier (just think about all the operations required to render just one pixel of your rotopaint output - every rotopaint stroke is actually one or two more nodes in the internal graph): http://natron.readthedocs.io/en/rb-2.3/plugins/fr.inria.built-in.DiskCache.html
In any case, clearing all caches should be preferred over manually changing parameters back and forth.
Windows OS at work. I will try Linux at home this weekend.
Clear all cache just didn’t work a lot of time, that’s why I have to manually switch lifetime of rotoPaint node.
Disk Cache node seems to be a good work around, definitely better than rendering out roto matte.