For the first time, on installing a new motherboard, fitting the cooling fan caused it to bend. I didn't notice initially because, naturally, the board was screwed into the case first. On developing frequent, random faults I removed the board to discover that the standard AM3 cooling fan had caused it to bend.

This is not tolerable in industry though many self-styled computer experts say it's fine "because the PCB is fibreglass". It matters not if the filler is epoxy or polyester resin, it's likely to damage some of the very fine tracks, including those in unseen, middle layers, and also to pop the end off SMT components, especially the tiny ones resembling a grain of sugar which, I think, are decoupling capacitors.

My cure was to discard the heatsink bracket fixings (a basic 2-part set) and replace them with 5mm nylon screws and a 1mm nylon washer between the brackets and the board but I have also ordered a multi-part bracket set which takes the strain off the board.
Motherboard designers obviously don't want to keep much of an area clear for a "proper" bracket set so minimise the construction.

Operation is much improved but baffling at first because data written to the HDD was often corrupted so it wasn't obvious if faults lay with the HDD or the motherboard, especially if the faults were so variable.