Master styles crashes project in 7.0.4

Brand new project created with RW 7.0.4 and every time I click on Master Style I get the “somethings gone wrong” box. Error report doesn’t work and sure enough, if I stay on the project it starts to hang. Have tried in a number of themes and same every time.

Went back to RW 7.0.3, opened the same project (i.e. created in 7.0.4) and same thing happened.

Now recreated the project in 7.0.3 and open in 7.0.3 and all is OK

Can we get a fix for this please.