STM32L4: Bootloader Jump to App fails depending of optimization level

Hello,

I am trying to write a bootloader for STM32L496(ZGT) and I am pretty new to ARM and RTX.
The Bootloader works over USB HID and uses RTX5 (RTOS 2).
I use µVision V5.36 with compilter V6.16 (With AC5 like warnings).

I encounter a strange behavior.
If I use optimization level o0 my Jump function "failes". I jump but get stuck in the main app. As far as I know at some point where some IRQ should be disabled.
If I use level o1 it jumps.

My Jump funcion:

typedef void (*pFunction)(void);

void JumpToApplication(uint32_t uiAppAdress)
 {
     uint32_t JumpAddress = *(__IO uint32_t*)(uiAppAdress + 4);
     pFunction Jump       = (pFunction)JumpAddress;
 
     HAL_RCC_DeInit();
     HAL_DeInit();
    
         NVIC->ICER[ 0 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 1 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 2 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 3 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 4 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 5 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 6 ] = 0xFFFFFFFF ;
         NVIC->ICER[ 7 ] = 0xFFFFFFFF ;

         NVIC->ICPR[ 0 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 1 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 2 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 3 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 4 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 5 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 6 ] = 0xFFFFFFFF ;
         NVIC->ICPR[ 7 ] = 0xFFFFFFFF ;
        
         SCB->ICSR |= SCB_ICSR_PENDSTCLR_Msk ;
    
         SCB->SHCSR &= ~( SCB_SHCSR_USGFAULTENA_Msk | SCB_SHCSR_BUSFAULTENA_Msk | SCB_SHCSR_MEMFAULTENA_Msk ) ;
    
     SysTick->CTRL = 0;
     SysTick->LOAD = 0;
     SysTick->VAL  = 0;
 
     SCB->VTOR = uiAppAdress;
 
         __set_CONTROL(0x00000000);
    
     __set_MSP(*(__IO uint32_t*)uiAppAdress);
     Jump();
 }

Maybe anyone has an idea why it get stucks?

Thanks Stefan