Losing connection with JLink on STM32H743IIK6 with Zephyr 2.7.2

[ghost]

Hi,
I am working on STM32H743IIK6 based custom board by porting it to Zephyr v2.7.2 and running it at system clock of 475MHz.

First, I tried building the bare metal sample example such as Blinking of LEDs (generated from STM32CubeMxIDE), it just works fine without any issue. I am able to connect and disconnect to the soc on JTAG through STLink and JLink Seggar as well, even before or after flashing the binary. Also, I am able to reprogram and erase it multiple times with or without power cycle.

But with zephyr, even though I am not getting any exception or firmware is not crashing-
Observation 1:
When tried building a firmware for the zephyr/samples/basic/blinky, even though it jumps into the main() and I can see continuous blinking of the LED, I am losing the connection with SWD (Serial wire debug) i.e. JTAG pins. Here, I cannot connect back to the soc through SWD and in turn cannot erase or reprogram this soc again.

Observation 2:
When tried building a firmware for the zephyr/samples/net/civetweb/websocket_server (which has a logic of creating threads), it jumps to the main() but after 90-95 seconds, but does not assign static ip to the soc.

Any leads or help on where I am doing wrong OR existing observation / issue with STM32H743 compatibility or Cortex M7 core with zephyr.

P.S.
I double checked that I am not overwriting SWD pins anywhere and kept a bare minimum device tree config (dts) such as UART, LED, Clock and Flash.
I also checked pin states of SWDIO, SWDCLK and SWRST pins on bare metal and zephyr based codes, but there is no difference with respect to before, after flashing or power cycle scenarios.