Unity -> Cannot print apk with "Error: MethodHandle.invoke and MethodHandle.invokeExact are only~" when building a release on AndroidStudio

Unity 2017.4.10 f1
Admin:Google Mobile Ads Unity Plugin v3.15.1 (latest)
AppLovin: GoogleMobileAdsAppLovinMediation-4.0.0.zip (latest)

In the above environment, modify build.gradle and Manifest as appropriate on AndroidStudio after exporting gradle build.

Now I can output up to the debug apk without any problems.
However, if you try to print an apk for release.

This error occurred.

Error: MethodHandle.invoke and MethodHandle.invokeExact are only supported starting with Android O(--min-api26)

As per the error, if the minSdkVersion is set to 26, it will succeed.
As it is limited to Android 8.0 or higher, I would like to set minSdkVersion to 19 or higher at least, but
Is there any way?

(If you output an apk file in debug, the app will run without any problems with Android OS 7.0 devices, so
I looked into various solutions, but I couldn't find them, so I'd appreciate it if you could help me.)

Tried

• Cannot build directly on unity, internal, gradle build, custom gradle template, etc.
• I have tried various versions of SDK, JDK, and NDK.
• Adjusting maven and gradle versions of build.gradle, adding groovy:groovy-all, etc.
• Is it possible that you are using the Invoke() method on Unity?