For those that are reading this and wondering what happened. it seems that 2018.2 has fixed some memory issues, after upgrading to the version we have not encountered a problem. In addition, if we had 2018.1 then upgrade to 2018.2 then back to 2018.1 - issue did not exist (not sure why).
I am getting the error: Invoke Process workflow: The activity ‘Invoke TessRactExtract workflow’ with ID 19 threw or propagated an exception while being canceled.