I did following steps to downgrade Gradle back to the original version:
- I deleted content of '.gradle/caches' folder in user home directory (windows).
- I deleted content of '.gradle' folder in my project root.
- I checked that Gradle version is properly set in 'Project' option of 'Project Structure' in Android Studio.
- I selected 'Use default gradle wrapper' option in 'Settings' in Android Studio, just search for gradle key word to find it.
Probably last step is enough as in my case the path to the new Gradle distribution was hardcoded there under 'Gradle home' option.