When I use a clone command in a command block and then activate the command block the selected area continues to be cloned all the way to unloaded chunks. This only happens in south and east directions. Here is a video about it: https://www.youtube.com/watch?v=B18zN11Q-mQ&t=0s
Thank you for your report!
We're actually already tracking this issue in MC-155690, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.