Thank you. I worked through these suggestions but they did not resolve the issue. I was using 2 different browsers to test this. I then decided to use a third (new) browser (in desperation). I found that the issue was not present on the 3rd browser, which suggested the problem was browser related. So I went back to the 2 original browsers and cleared the history and all cookies. This resolved the problem.
Old version worked. No spam. Now being bombarded with spam since upgrading. Can this be fixed urgently or rolled-back?