Awaiting your results;)
But: I've been testing some more here since I never had to start rendering an animation from another frame than the first. I wrote to you that my animation renders alright if I set the frame to start with to something else and then it renders with the index adjusted. Now I had a closer look and though mb3d starts the filename at the number I entered (+1), it starts at keyframe 1.
So suppose I have an animation of 4 keyframes in the animationmaker, and each keyframe has 50 subframes. That makes 200 frames total.
Now if I set the index to say 37 and hit Render!, the rendered images will be called blabla000038.png, blabla000039.png, blabla000040.png, to blabla000240.png. That's where you think Hey, 240? And that's because only the name of the frames changes, but the program just renders from keyframe1, which is also frame1. In short, there's no way it can Really start to render from frame37, it will always start at frame1.
Now, in the Preview you can set it to start rendering at a certain
KeyframeMy m3a was not a good one to test as all three keyframes look the same
In the one I attached you can try and have the preview start rendering at keyframe2 or 3, to see what happens.
Resume: Resuming an animation render from a certain frame is not possible (a limitation of the program as it does not seem to write the needed information to the m3a file), but it is possible to render from the next keyframe by loading the m3a and then tossing out the keyframes already rendered with their subframes. Which means that it's a good idea to use more keyframes, and if you stop rendering halfway, let it always render until it comes across the next keyframe so you can resume from there at a later time. And Then setting the index to the right framenumber is a good idea to prevent overwriting;)
Still there seems something very much amiss with your m3a-file, and I do not think it's a bug of the program. I have saved your two keyframes to .m3i-file, closed mb3d, reopened the program and loaded them into a new animation and it renders nicely, not only the subframes from keyframe1, but also those of the second. If you do the same you can at least render the whole animation again.
In the enclosed version of m3a-file you can test the 'render from keyframe'-possibilities. Also, kick out the first or first two keyframe and see what happens, if you like;)
The whole thing when rendered looks like this