Solution to frozen time machine

i was attempting to restore an old version of a file from Time Machine database located on external hard drive. Several tries all ended with frozen user interface and no luck in seeing or restoring the missing file. External monitor was connected. On last try I disconnected the external monitor, restarted the Mac (MacBook Pro early 2015 running latest version of OS) and tried to enter Time Machine again. The timeline interface popped right up and I was able to restore the missing file. Huge sigh of relief!

-Bill