i have a process model as attached , my aim is to show the user input task (UI)

AS per my understanding below are the points that might be breaking chaining in your process model
1. You have 'Execute process report' node in process model before user input task, which might be taking long time to get execute and breaking the chaining.
2. All nodes in 'Get Repayment scanned Document' sub process should be chained.
3. Sub process should not have any node which required to be wait (e.g. times event, user input task)
And one more thing that I have observed in your process model is, you can probably remove parallel flows and 'And' gateway as it seems that both flows are assigned to system. (Assuming that Get repayment Document does not have user input task)
PFA screen shot which depicts the PM after removing parallel flows and ‘AND’ gateway

AS per my understanding below are the points that might be breaking chaining in your process model
1. You have 'Execute process report' node in process model before user input task, which might be taking long time to get execute and breaking the chaining.
2. All nodes in 'Get Repayment scanned Document' sub process should be chained.
3. Sub process should not have any node which required to be wait (e.g. times event, user input task)
And one more thing that I have observed in your process model is, you can probably remove parallel flows and 'And' gateway as it seems that both flows are assigned to system. (Assuming that Get repayment Document does not have user input task)
PFA screen shot which depicts the PM after removing parallel flows and ‘AND’ gateway