I had the same experience on one machine (Windows 7) after the 7.1.5 update but, curiously, not on my laptop - local adjustments are not something I use very often, so I'm not sure if the update had somehow reset the defaults on that machine or whether it had been like this for a while.
You need to go into the Local Adjustments tab and click on the down arrow on the right of the toolbar for each local adjustments tool (e.g. Exposure). At the bottom of the dropdown menu that appears, check 'Adjust Selected Layer'. The menu will then close and you should see a little paintbrush appear immediately to the right of the tool label. The tool will then work on the selected adjustment layer only, as expected.
It took me a while to work that one out, and I've been using C1 Pro for years ...