Some follow-up thoughts..

It seems as though the PLC is repeatedly switched off/on. I am not sure if this happens by user choice or is the PLC doing so on its own. Please clarify.

I observe that the messages are complaining that the analog card reading is extending its boundaries. 

(powered off state)  Plug out all signal boards and signal modules. Attempt to boot up the PLC. On the extreme keep only the power connection to the CPU and disconnect all other wiring (do it safely! avoid shorting wires). Confirm that the PLC is able to boot up. Make hardware configuration changes that matches the bare CPU. Confirm the CPU is without error.

(powered off state) Plug in all hardware components (CB / SB / CM / SM) and wiring, except the problem analog card. Confirm that the PLC is able to boot up. Make hardware configuration changes that matches your configuration. Confirm the CPU is without error.

(powered off state) Next phase is to put back the analog card. Only supply power to it where required and disconnect the signals. If the configuration is for 0 - 10V measurement: connect every channel's signal +input and -input pin together. Confirm that the PLC is able to boot up. Make hardware configuration changes that matches your configuration – make very sure the configuration is loaded properly. Confirm “280” is the resource number for the analog card. Confirm the CPU is without error.

If you have success up to this point, put back the original signal wires only after you determined that the signals does not exceed the measuring ability of the analog input (as configured by the hardware configuration). Keep the spare analog inputs channel's +/- pins (per channel) shorted to each other to prevent drift. 

Share your method and findings with the Support Team when you “speak” with them.

I am glad you eventually followed my initial advice to contact Siemens Support.

I further appreciate you posting back your results even though it was not a positive and satisfactory result - yet.

alanTI

This ha finally bothered me enough to open a support ticket.

It looks like it is a bug, no solution provided besides waiting the next fw release. 

Siemens support

I checked this and found out that this topic was already investigated by development. According to the current information, this is improved with the next firmware version V4.1.x that is planned for Dezember 2025.

Note:

In this case the firmware change is from V1.0.x to V4.1.x

With this the new S7-1200 G2 hardware and current S7-1500 have the same firmware numbering.

 As additional info I have deployed 5 of these 4AI SB, so far 2 have developed this problem.