Default [Q] back key & recent key not working in xperia ray

After flashing xperia overlay..around 2-3 days later my back key and recent key suddenly stops working.
I thought it was minor issue so i just flashed the stock firmware but issue not solved.
then i again root my device and try some onscreen keys application..but it also not worked.

what happened to my device...it wasn't wet, dropped or anything else.

Xperia ray st18i
4.1.B.0.587
Sony Xperia M C1904 Rooted/Unlocked Bootloader
Unofficial AICP
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