After upgrade the EX4100 switches from version 22.4R3.25 to 23.4R2-S5.8 the devices stuck in the “can’t load kernel” state.
Please perform format installation into the target version and check the status.
If the format installation was failed then perform format to the previous version 22.4R3.25.
Once the device recoved in the previous Junos code.
We can upgrade the device into major release of 23 version followed by that we can upgrade the switches into the target version