Caterpillar 3406 b/c engine problem

General Truck Information:
Peter Bilt dump truck with a first-generation 3406 B/C semi-electronic engine with hydraulic injectors.

Problem Description:
When starting the truck in the morning, it starts quickly. The low oil pressure is 60 psi and the RPMs are between 600 and 700. If the engine doesn't stall after starting, it runs smoothly throughout the day. When the engine reaches its optimal operating temperature (180°C), the oil pressure drops to 40 psi and the RPMs are between 1400 and 1500.
If the truck stalls for any reason, it begins to malfunction when restarted. The symptoms it presents are the following:
1. It starts to oscillate
2. The CHECK ENGINE light comes on
3. Code 24 flashes.

After 5 minutes of these faults, the engine shuts off automatically. If, after shutting off, the ignition switch is turned to the off position and an attempt is made to turn it on again, the machine starts without any problem. If the fault does not occur again within an hour, it will not occur again for the rest of the day.

The truck doesn't emit smoke, doesn't consume excessive diesel, and has received all scheduled maintenance services, including:
1. Oil change with Mobil 15W40 oil;
2. Replacement of both diesel and oil filters with original parts;
3. Cleaning of ECM connectors to all sensors;
4. Replacement of the oil pressure sensor with an original part.

This truck was purchased in the USA eight months ago, tested, and presented no issues. The seller stated that the engine had recently been rebuilt, but the restart test was never performed. The engine had been sitting unused for a year without a battery installed.
Upon arrival in Mexico, it began to malfunction while driving. The cruise control then stopped working, and after several months, the engine brake also failed. The engine brake works intermittently and then stops working for several days at a time; this problem is unstable.
The system was scanned and only one old stored code, code 24, was found, along with an active code, also 24. After detecting these codes, they were cleared, and the batteries and sensors were disconnected for 4 hours. After this time, the engine was restarted and showed no problems. When the machine was restarted again in the morning, code 24 reappeared, and the engine shut off automatically.
In addition to the scheduled services, the following inspections were performed:
1. The oil pan was removed, and the oil pump strainer was inspected and found to be free of impurities.
2. The pressure relief valve was removed; it showed a slight discoloration in the middle section, from a mirror finish to a dull, almost as if it had been scraped with a very fine file.
3. Washers were placed between the spring and the plunger to provide a little "back pressure" on the relief valve. It was closed, and the engine was started. The pressure rose from 60 to 75 psi when cold and from 40 to 45 psi at optimal operating temperature. The engine speed was then regulated to 1800 RPM, as it was not previously regulated.
Even after these checks and minor changes, the engine continues to stall. The temperature never exceeds 190°C. The fuel lines and diesel tanks were cleaned.
Question:
This type of pump operates using the engine's internal pressure. If there were an internal oil pressure leak in one of the pump seals, could this cause the ECM to interpret it as a serious problem of low lubrication pressure and trigger the engine shutdown signal?

Note:
The physical gauge shows good oil pressure when the fault occurs, yet the display shows code 24. If the physical gauge doesn't match the flash code, what does code 24 indicate?
Which of the two gauges is correct and which is incorrect?