Engine 2007 4.0 No Oil Pressure

I have a 2007 4.0 v6. Engine was rebuilt and after many timing chain tensioner issues was running fine. Last week engine oil pressure light and gauge report no oil pressure. Oil was just changed two weeks prior, checked again and was full. Replaced oil pump. pan was clean as a whistle. engine started fine, oil pressure came up. no problem. About five minutesg later oil pressure dropped to zero.

Ford dealer says issues with oil pump drive shaft can fatigue and then jam. Replaced it. Same results. starts fine, pressure is good then disappears.

Going crazy. Any ideas.

We have researched some of the explorer engines and oil pressure issue. Replaced the oil filter in the hopes it was bad. No luck. Car starts fine, runs fine for five minutes or so, then oil pressure disappears and engine starts tapping. Nobody has heard of this issue?? Any 4.0 mechanics that can give us an idea what the oil system process is and what we might be missing???

Okay, five weeks and counting. Pulled the oil filter holder off the block and replace O ring on that bolt. No Luck. Ran engine, it start fine, sounds good. after 5 minutes, pressure gone, tapping sounds. Shut down engine, five minutes later start up, plenty of pressure, then cycle repeats. ANy IDEA???