Rotobrush 2 Standard/ best

Hi,

I shot something at 59.94 frames per second and I changed the setting in Composition settings to 24 frames per sec for the convenience of render timing.

I get stuck in some frames where I can't add or subtract the rotobrush and the error shoes that I had changed the original frame rate and also that, I have to wait till the current frame is rendered (Which is already rendered because no matter how much time I wait, it shows that the rendering is over but the error claims that the frame is still rendering when I try to add or delete areas with the rotobrush)