Thanks, for you responses
R7R4 on the back of the board is also bridged.
The XBox boots the same way when pressing the power button or when holding it for at least one second or by pressing the eject button or holding it for at least one second.
I've also started BiosChecker on every run and it also showed always the same.
As far as I understand it always boots into the ModChip.
I've attached to output from BiosChecker
I found a wiring diagram for this particular ModChip (Aladdin2 V 1.0-1.1 Diagram), but BT is soldered to a different location (On my XBox to ground).
So, in my understanding, BT is the reason why the XBox always boots from the modchip and if I desolder BT the XBox should boot from the TSOP.
Can I damage the XBox when trying to boot from the TSOP?