Might have spoken too soon. After entering the openocd - f... (which got the system talking again), it then failed again and I hav enot been able to recover it yet. What might be of interest is that running openocd from the command line makes it clear what error messages are being thrown: Info : acc...

Thank you Gardin. You would not believe the man-weeks we have wasted on the how fragile the IDE system. It doesn't seem to matter which IDE we have used: Eclipse, Espressif-IDE, PlatformIO, VSCode - the system will work fine for a few days and then simply stop communicating with the debugger. It has...

To help anyone finding this later, EFUSE_STRAP_JTAG_SEL is 0 be default, not 1 as per the OP. By default, GPIO3 is ignored.