There were some versions where the edit answer options didn't show. Can't remember which versions this concerned.
But like Denis says: It does not make sense to try to troubleshoot an installation that is completely out of date. If it is a bug in that version, it probably has been fixed a long time ago.
Version 3.15.1+181017
Your version was released on 17/10/2018, so it is now 4,5 years old and hasn't received any bug fixes, security patches or updates in general. I think it is time for an update to the latest version of LS3 at least. Then you can check if the error persists and we will try to figure out why.
Because this definitely doesn't happen normally in recent versions of LS3.