I don't know much about BPML but I know Camunda (https://camunda.com/) does stuff in BPMN. Sorry if that is not the same.
67 karma · joined May 21, 2021
So I would still expect you to pay if the dev struggles, unless the dev doesn't do a good job explaining why they are struggling.
See this link for an example with some highlights (1 minute): https://youtu.be/5o71pRZ-aMk