How to fix an error when connecting to an AdMob project?

Question

Java

I have an application - it worked without errors. Connected AdMob according to the instructions. Errors in statistics began to pour massively:
java.lang.NoClassDefFoundError:
at ly.b ([email protected]@20290004.249178941.249178941:2)
at lx.a (com.google.android.gms.policy_ads_fdr_dynamite @[email protected]:1) at
lz.a at lc.a ([email protected]@20290004.249178948.241917
)
at lc.run ([email protected]@20290004.249178941.249178941:2)
Caused by: java.lang.ClassNotFoundException:
at dalvik.system.BaseDexClassLoader.findClass (BaseDexClassLoader.java:134)
at java. lang.ClassLoader.loadClass (ClassLoader.java:379)
at ab.loadClass ([email protected]@17.7.85 (100408-253824076):4)
at java.lang.ClassLoader.loadClass (ClassLoader .java:312)
The problem does not appear on my device, so it's not clear how to fix it. Has anyone seen this kind of effect?