Debug stays at Reset_Handler, step into/over buttons are disabled
their are some thread here and how to on the net for rtos aware debug.
basiclay
you need to add a line on the openocd cfg
add a variable in your code (free rtos compat) for debugger to catch it
and voila.
likley your reset problem was h/w or that reset cfg.
i personaly used nucleo,discovery and a few custom baord with standard openocd cfg and almost never change configuration.
;){kind=link}