Suggest you to do following two things and check if this resolves the issue:
1.Select the brush tool and open tool options in lower action panel. At the right end, see for the flying widget. Open it and click Rest tool:
2. Reset application preferences. For this, press Ctrl/Cmd +K . Click on Reset preferences on next launch , click OK and restart the PSE.
Please let me know in case this doesn't work for you.