I have just hit this same problem today @George
If my action is very simple, a multi database query, which returns 1040 records.
Then a repeat step pointed at the actual query, and a single setvalue in the repeat for testing purposes it works perfectly.
If I then add a step to include a library action then i get the following error., if I remove the include, it works again.
{
"status": "500",
"message": "core.repeater: repeat is required.",
"stack": "Error: core.repeater: repeat is required.\n at App.parseRequired (/opt/node_app/lib/core/app.js:524:23)\n at App.repeat (/opt/node_app/lib/modules/core.js:18:29)\n at App._exec (/opt/node_app/lib/core/app.js:491:57)\n at App._exec (/opt/node_app/lib/core/app.js:458:28)\n at processTicksAndRejections (node:internal/process/task_queues:96:5)\n at async App.exec (/opt/node_app/lib/core/app.js:427:9)\n at async App.repeat (/opt/node_app/lib/modules/core.js:80:17)\n at async App._exec (/opt/node_app/lib/core/app.js:491:30)\n at async App._exec (/opt/node_app/lib/core/app.js:458:17)\n at async App.exec (/opt/node_app/lib/core/app.js:427:9)"
}
Edit: Even if I remove all previous steps, and only use the include pointed at a library action which itself contains many repeat steps, I get the error. The same happens for the Execute step. So something pretty strange going on with this.