Spun cam bearing...

Hello

I am curious what could have caused my camshaft bearing to move?
Bearings are not new, they were installed like 12 years ago.
I was currently using solid roller billet cam, it was 4th different camshaft in this block. I was regularly spinning to 7000...
All other bearings are in place and look good, it’s almost a shame to remove them ;-)
I caught this early so cam was not affected. Rockers took the biggest beating but they can be reused.

I will be installing new bearings and wanted to know how to avoid this in future?

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