The problem some are having is that the canister which surrounds the filter is moving inwards, and the O ring is not sufficiently compressed. If it moves far enough you have little, if any, oil pressure.
It is a simple matter to measure the setback and the 0 ring thickness and shim accordingly
Antons site explains the problem, and the solution, and if anyone is unwilling to read it, or has read it and dont understand it, it is probably better if they refrain from giving others advice.
When I bought my R100 GS it had been serviced 300 km before by the states only BMW dealer.
I like to give anything I buy a full service right away and luckily made no exception this time .
There were no shims and a gasket and the O ring had so much space it actually had a twist in it.
It took three shims and the removal of the gasket to get less than 1mm compression on it.
One good long hot run and that engine would have been toast, so the advice to put back what I found would have been a disaster.