I am having a very similar issue. I have tried multiple different things to eliminate other possibilities but every time I try to delete a wall in build mode the game freezes and I can't do anything ...
Ideas
Status changed:
Troubleshooting
to Reviewed
Thanks.
There's a known issue where changing build mode generally leads to issues: Can't make changes to build | EA Forums - 4976886 but leaving this separate as it sounds it's specifically walls.