Thanks both!
@orvalman - +1 on tool-openocd needing updating in platformio and thank you for creating that issue 
Summary & reason for close
The version of tool-openocd bundled with platformio is not up to date and causes some functionality to misbehave. @orvalman has created an issue in the platformio/platform-ststm32 which should hopefully be resolved soon.
In the meantime and from both our experiences - using configuration files based on the latest version of openocd and overwriting platformio’s ones is likely the best route to success.