We were doing same changes in manage jenkins -> configure system page. While saving the configuration , it took a long time and we got a error page mentioning "oops. a problem occured while processing your request." . 

Post this error , if we refresh the configure jenkins page, we are not able to see few of the congurations which were present at the bottom of the page. Even apply/save button and the jenkins version which was present in the footer is also missing. 

Jenkins version : 2.263.1

Kindly help us resolve this issue.