The effect seen on the showcase video at 2:48, which you can see here: https://www.youtube.com/watch?v=4rGkxLnKmn8&feature=youtu.be&t=168 does not happen under any circumstances. Even with the additional falling blocks enabled:

Additional Falling Blocks:
    Enable: true
    [...]

And all cave-in features toggled on, the effect seen on the video cannot be done. When a dirt block is broken in a cave entrance or cave ceiling, only the block directly above the broken dirt falls. The blocks are subject to gravity, but they don't make the surrounding blocks of the same sort to come falling as well.

Dirt and grass, which is often compacted into a solid mass in cavern ceilings and floors, will also come crashing down when disturbed.

I'm running latest EHM and Paper. Apologies for English mistakes.

Can you provide a video or screenshots of what's happening on your end?

Am assuming it's just grass blocks that are affected? If so then it should be fixed by now. Let me know here otherwise.