Cannot create new site page by choosing saved template

I am trying to create a new site page, however i am not able to save the page by using save as draft nor able to publish it.

The page keeps on auto saving at the back end and creates multiple copies under site pages.

Inner-Message: Invalid data has been used to update the list item. The field you are trying to update may be read only.

Exception-Message: We're sorry, we encountered an unexpected error. Please refresh the page and try again.

Refreshing the page does work out, but it removes the web parts in the saved template, which is not helpful.

can anyone please help me with this.