What can cause new motor mounts break in 6 months?

I have a Honda crv, the car had some rumbling noise whenever it start moving from idle, my mechanic told me motor mounts are broken and I had them replaced all the mounts ( 3 motors, 1 transmission).

But then less than 6 months later, the left and right mounts are broke again.

And so obviously what they sold me aren't very good quality dispite they claimed they're top quality.

But my question is, even if the mounts are cheap, what are the things that could break new mounts in 6 months?

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