Git submodule update error SITL using vagrant

Hi. Hoping someone can help. I am trying to get SITL up and running on my MacBook using vagrant. I get as far as running submodule update but get following error …

vagrant@ubuntu-bionic:/vagrant$ git submodule update --init --recursive

error: could not lock config file .git/config: Protocol error

error: could not lock config file .git/config: Protocol error

fatal: Failed to register url for submodule path ‘modules/ChibiOS’

thanks