Not able to save child table data from parent doctype

I have created a doctype with child table. When I tried to add entry, it does not save child table data on save.

I have observed one thing using debugger that, it contains child table values in before_save event but when it reaches to after_save, it clears the child table array.

I am using below frappe versions.

erpnext 13.17.0
frappe 13.17.1

Can anyone please let me know how can I solve this issue?