Lightning Error and "Preview" Shadow

I press the build Button and this came can somebody help me i am also using the flex version if that help and i mean its not that bad i can work with it but it would be cool if i have accurate shadows :smiley:

Try selecting build lighting only from the build menu and it looks like you are getting a swarm error, do you have swarm installed or customized in any way besides the default?

I made some changes after researching online for this error but made everything to normal after it dont worked and is it may installed coase flex could this be?