There were some 6 layouts under Availabe Default layouts. Are all missing now.
But when I tried to create a new Layout with the same name it shows the Layout already exist.
How can I make the existing layouts visible?

And on Theme Builder >> Backup I am getting an error as below:
A system error has occurred — our apologies!
Cause
javax.servlet.ServletException: Servlet execution threw an exception
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:313)
caused by: java.lang.StackOverflowError
at java.util.concurrent.ConcurrentHashMap.get(Unknown Source)