The biggest mistake IMO is to use an agile BPM and turn it into an IT project right from the start. Many times programmatic integrations with external systems are coded right from the start. Business process systems are agile. But when you integrate custom coded integrations too soon, then you can't leverage the agility of the BPM system any more. Custom coded integrations are not easily changeable.

Better is to focus on the people first. First coordinate the people, automate the handovers and escalations. Business people can do that with today's BPM systems. As long as the process only deals with handovers and escalations, it's easy to change.

After that process has matured and it is stable, then custom build integrations with other systems make more sense.

So my advice is to consider 2 separate phases when automating a business process: First coordinate the people. Make the most of the BPM system flexibility. And when that is clear and stable, only then build custom coded integrations. You will save many precious developer cycles.