I had the very same problem on an older G2 grand. I sanded hammershanks down with a one inch taper or so. I then wedged them into the gap with some wood glue. I have also used small thin maple shims and hammered them up to fill the gap with some glue. Stability will improve imediately or something else is wrong. I did not wish to up and over the piano and fill with epoxie. The cure was recommended by a Yamaha tech and it did the trick. You need a shim every inch or so. Ed Tomlinson
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