Steinway M Backcheck Problem

[AlliedPianoCraft]

I am regulating a 10 year old Steinway M with all original action parts. I am having a problem with checking. The piano checks 100% on the bench, but no checking at all in the bass section and 85% OK in all other sections.  I have adjusted the angle on the backchecks with no success. Does anyone have any thoughts on what the problem my be and a possible fix?

Al Guecia
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