Error "Invalid client task found corresponding properties" only when triggered from workflow ?

Error "Invalid client task found corresponding properties" only when triggered from workflow ?

Hi All,

I am facing an error message I never encountered previously: 

  1.     Error in executing On Add - On Load script
  2. Error in executing thisapp.get_all_projects_api_call function. Line:(2)
  3. Error in executing thisapp.getAccessTokenFromRefreshToken function. Line:(6)
  4. Invalid client task found corresponding properties Line:(39)

When I manually run the function "getAccessTokenFromRefreshToken", it runs without any issue. So I am puzzled. 
I printed (through "info" the returns of the different calls, and everything looks good. The issue seems to be with a line where I assign a new collection value to a Collection Variable (env. variable):

  1.     thisapp.variables.api_connection.search_access_token = {"token":response_token.getJSON("access_token"),"validity":now.addSeconds(3600).toString()};

The most annoying part of all that is that it only happens when the function is triggered from a workflow. It works fine when triggered directly.

Many thanks for the help.
Kind regards,

Guillaume