Stack pointer gets corrupted in debugger

Hi everyone

I am usinng the NXP KL43L256Z4 Cortex M0+, compiler MDK-ARM uVision V5.25.2

When I am in a breakpoint, I change any register value (ex. R6 = 0xFFFFFF), in the next step the Stackpointer R13(SP), gets always the 0xFFFFFFFC value, does not matter where point in the program it is.

Current values:

R13(SP) = 0x1FFFE460
R0 = 0X000000

Breakpoint                CPSID   I               ; Mask interrupts
                LDR     R0, =SystemInit
                BLX     R0

Here I insert into R0, 0XFFFFFF

in this moment the SP become: R13(SP) = 0x1FFFFFFC

Somebody saw somthing like it? It is a KEIL error?

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