mrystry shield generator appear out of nowhere

it's stopping me from decorating my ship

 

You should be able to turn off the Shield Generator, both the generator object and the lever.
If that doesn't work, you will probably have to resort to admin commands.
You'd have to:

1. Use /admin to be able to use commands.
2. Activate /debug to find your dungeonID
3. Use /settileprotection [dungeonID] false to turn off tile protection. (works for all dungeons. You can set it back to true afterwards.)

After that you can deactivate debug and admin mode again.