I don’t know what the issue is (assuming disk space is not an issue).
But I wonder about the merit of the Action itself.
If the same painting steps are being performed on each image might not an approach involving placed files be more efficient? (Haven’t tested that, though.)
You might want to try thowing in a "purge all" command in your action.
Reading c.pfaffenbichler's response makes me also think this could be done better. I'm not sure what you're trying to do to each frame, but is it something you could do to one frame above your main clip to create the change for all the frames?
but is it something you could do to one frame above your main clip to create the change for all the frames?
I do very little video editing, so I did not think of this, but it may well be the easier solution by far.
And even if the brush strokes were done with different Blend Modes the effect might be possible to be emulated with a couple of Layers.