TDA4AP-Q1: After powering up TDA4 device does not enter DFU mode

Part Number: TDA4AP-Q1

Hello,
on our design we want to connect the TDA4 via DFU mode to PC. Unfortunately this worked only for one device for the others obviously same HW setup there is no detection of the USB device from PC side.

We already checked:
*Power rails are stable and PMIC signal deliver expected values (SOC_PORZ high, MCU_PORZ high)
*For TDA4 side
--the RESETSTATZ, MCU_RESETSTATZ are going to high after power up
--Crystal for OSC0 is switched on and oscillating at its nominal frequency
--MCU_SAFETY_ERRZ, SOC_SAFETY_ERRZ, RESET_REQZ are all high
--The USB0_VBUS signal is around 1.8V on all devices when a USB A-A cable is connected.

On boards that cannot connect the current consumption on 3.3V rail that powers TDA4 parts there is lower power consumption (around 800mW less) to the one with DFU mode enabling.

Questions:
1. What else can we check to ensure that the Processor is really running and ready to enter the DFU mode?
2. Are there other possibilities to connect to the processor at this state e.g. JTAG/Debugger, other boot options?
3. Which rails would be interesting to check for current to see there a difference for the current consumption?
4. Generally, what could be root causes that this does not work?

Thanks for your answer in advance
Kind regards
Thomas