Step 5 immediately CPU stop

During following days multiple trips occurred and in each of them at least one of the CPUs went to Stop mode with needs to Cold restart. It may be useful to mention in all these cases stop led on CPU was blinking and BASP led was lit except for the last trip that in one of the CPUs the ZYK Led was lit too. In each of the stop conditions we gather the information of IStack & BStack of stopped PLC that have been attached to this thread.

In addition to above investigations, we have changed some of hardware to rectify the error without any exact reason and only some guesses, for example we have changed the extension rack Power Supply, as we had an experience of failing of it in another similar package. Also we have changed the Power Supply modules in CPU racks, one of the CPUs and two communication modules that connect the CPUs together for redundancy.

Although all mentioned activities the problem has not rectified and we have no idea to start with. Would you please investigate the situation and help us with your respectful advices.