I had this problem prior to the MCUX 10.2.0 upgrade but it seems to be cropping up more now.
I'm using a P&E Cyclone ACP as my primary debug interface. P&E recently made some updates that really helped the stability - it no longer hangs if you just reset the target board or disconnect the cable, for example - but it's still failing sometimes and they're blaming it on the gdb side.
On four different boards today, of two very different designs (all based on the MK22FN1M0AVLH12) I've had the debugger just stop doing anything. I'll launch the application and if I let it run and hit pause, the debugger is no longer responding. I have to kill the pegdbgserver_console.exe process before I can launch it again, and until then none of the debugger controls in the IDE do anything, including the terminate button.
If I put it in instruction stepping mode, I can step through until the WDOG unlock and then it jumps back to the entry point. That's not really surprising since it's a two-part update, but if I put a breakpoint on the other side of the WDOG setup it never gets there. For that matter, if I put a breakpoint at the second instruction it never stops there, either.
I removed the WDOG setup entirely and then it doesn't seem to be getting past the MCG initialization. That could mean an oscillator problem, but I don't understand why the debugger just stops working when left to run.
Last time this came up the problem seemed to resolve, for that particular board, when I replaced the MCU. I've done that now with no change. I've got two identical boards here (barring any assembly errors - they're prototypes) and both were doing it initially, now one is starting OK. I dug up a TWR-K21F120M board and that seemed to start up OK.
I decided to give my LPC-Link2 a try. I'd never been able to get it to cooperate with earlier versions of MCUX - it seemed to have a conflict with the P&E setup - but 10.2.0 does a much better job of managing the interfaces. I fired it up and it programmed OK but got 'Wire ACK Fault in DAP access'. See the screenshot below. I get this with the TWR board as well, so it's not my hardware.
It's 10 PM and I'm giving up for the day. Any suggestions for tomorrow?