Have the same problem with just one 1/4 bit with a 1/2 shank. It's a Katana bit and every other Katana I have has no problems. Nor does any other bit.
I mic'ed it at exactly 1/2". Collet was cleaned and bit was not bottomed out.
I'm thinking that maybe it has something to do with heat, as I was routing some longish 1/4" deep dadoes.
It's infuriating, isn't it?
'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton
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