ThingWorx flow Custom Action

I have created a Custom Action by copying the existing HTTP Request Action and made some changes in the logic. If we use this Custom Action in a flow and if we try to save this flow, the flow is freezing and a status message 'undefined' will appear after few seconds. But if we check on the Workflow page after this, we will be able to see that recent flow but it can neither be edited nor deleted. On trying to open this workflow, after few seconds of loading it will go back to the main Workflow page.

I'm using ThingWorx 8.5.6-b110 -and ThingWorx Flow 8.5.6.

Kindly assist.