The 'dry' side of the diaphragm is vented to atmosphere and the centre of that fibre pump spacer should have been packed with grease on installation as a second line of defence.
How much above the 'max' level is the oil level?
If the oil level is way over the 'max' mark, the camwheel will dip into the oil, resulting in frothing and possible overheating.
Maybe also worth checking that the oil pressure switch isn't on the way out.
They seem to weep for a while, so that the oil pressure warning light flickers, before letting go properly...
ken