Please help.. Player falling through Landscape after adding new Landscape segments

Hi all, so been working on this sidescroller game for a while, everything was running flawlessly until tonight when i added two new sections to the landscape {manage - add}. In the photo it’s the bottom part of the map with the beach.

Anyway i was making that area and didn’t play for a while but now the player falls through the landscape wherever i place him. I haven’t touched any collision settings {As far as i know - Unless there’s a hotkey that can cause that}. Landscape is still ‘Block All’.

Can anyone help me resolve this? See Video for what i mean.

So i resolved it by using a backup save thank god. But then this also adds confusion. I bring the backup maps into the area where i keep my maps and rename them, except after renaming them they still show as ‘level1’ {my default map name}. Only when i click on the backup maps does the newly named ‘backupmap3’ appear. So i would assume i can keep that and delete the rest. But when i do that and only keep ‘Levelbackup3’ the issue of falliong through the floor returns.

I think this may be a bug, i was getting weird issues where i couldn’t move the sculpting brush around the map prior to this all happening.