Hello dzordzo

Event 5 (Event ID 16# 4531: STOP (memory reset request) caused by memory test error in memory submodule) is not to be ignored either (it is indeed the main message here).
If you select it in the Diagnostic Buffer and click on the "Help on Event" button you'll get the following information:

Cause:
During the memory area test on the CPU, a fault or incorrect function in the memory module memory card) or in the operating system was detected.

Effect:
This status is indicated by STOP and request for memory reset or by all the CPU LEDs flashing. In this status, the program is no longer executed and no further operations are possible.
Outputs are deactivated.

To correct or avoid errors:
You can usually correct the error by exchanging the memory module and performing a memory reset.
If all CPU LEDs are flashing, the CPU is operational again after turning it off and on again or, with more serious errors, after turning it off and on again without battery backup (in either case the CPU must first be switched to STOP).
The detailed information of the diagnostic buffer entry contains a hexadecimal code with the comment "No relevance for user". Note down this code and contact the manufacturer.
Make sure that there is not simply a mechanical problem by removing and reinserting the CPU.
The CPU is defective if the error occurs again after exchanging the memory module and powering on without battery backup.

I hope this helps