NorthWoodPecker

As long as the springs on the screws are compressed, the heat sink has contact.

Tighten a certain amount of revolutions per screw (1 or 2), then move to the diagonal opposite.
When the springs are compressed to 2/3 of when you started, I would say it's good enough.
(Eye measure should be good enough, but count the revolutions so you tighten them the same)

If you still get the error, loosen all screws 1 revolution and try again.

About the shorting, it's uncommon unless you have direct contact between the metal bracket and the PCB of the mobo - which I can't see why it should unless it's bend.

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