@pawel112 I was able to solve the similar issue mentioned above by increasing PHP memory limit from 128MB to 256MB.
I was able to solve the issue by increasing the PHP Memory-Limit from 128mb to 256mb.
After updating WordPress to 5.6, When I click the Update button, It gives Internal Server Error. Any Idea if this is because of incompatibility of version? Any solution? I can’t see the changes made to the page to be saved.