Cheapest thing to do - change the filter to a reputable high quality brand. High production, low cost filters can and have been a disaster.
No matter what the brand, a bad filter with loose internal parts does exactly what you describe -
oil pressure is all over the gauge, and you can lose a rod out the side of the block.
When the replacement motor started doing it too, 6 months later, I was told, change the filter to a good quality brand. I did, and it stopped immediately.
Until you change the filter - a $6 item - you can't be sure that it isn't the problem. But if it is, it can destroy a $6000 motor - or more.
Cost me $1,800 to learn that lesson, I won't buy inexpensive filters. And I won't buy my own house brand, it's the same maker.