Glad you enjoyed them.
Sounds like something is not right in the oil pressure circuit. The oil pressure around idle is low enough anyway at the best of times.
The oil pressure test will confirm if it is indeed low pressure (and not a faulty sensor/sensor circuit issue), and the necessity to start disassembling the engine again
Was there a lube issue previously, maybe related to why the engine had to be taken apart?
Or did the valve let go due to some other issue.