After further investigations reading the S32S247TV EVB schematics of motherboard and daughterboard etc, I could narrow down my problem to the soft reset circuitry:
After the debugger pulls the soft reset down (Soft reset LED is lighting up) it releases the reset. The expected behaviour should be that the LED should turn off immediately. But instead, it is still lighting with less illumination (i.e. some undefined voltage level, probably still LOW). After a while (may take several seconds), the LED tuns completely off.
I tried to remove all possibly unnecessary connections on the EVB by opening soft reset jumpers leading to unused peripherals, such as Ethernet and external flash etc. - still no success and the soft reset LED is still lighting dimmed.
Then I found the solution for me: I turned the EVB completely off and removed the S32S247TV from the die holder, then re-inserted again. After that, the soft reset LED immediately turned off after the debugger pulled the line LOW during debug init phase. Debug session could be established and everything seems to work.
--> So long story short: You can try to remove your controller form the die holder and re-insert. Maybe it helps to resolve your issue as well.