@dave1904 just coming back to this thread as @DownPW and I both experienced issues with other plugins today, and the fix was to use the plugin ordering in the ACP and move the Harmony theme to the very top so it comes before everything else in terms of other plugins.
It might be worth at least trying this to see if it gives you a result rather than the previous bulldozer approach. Thinking about it, the previous fix I proposed is along the same lines and disabling plugins does in fact change the order when they are enabled again, so this is definitely worth a try.
Let me know how you get on.
