could not generate key in keystore error

[skhugh]

When beta testing my app, one user out of around 1,000 users experienced "could not generate key in keystore" error and could not log in to my service with the following exception.

Caused by java.lang.IllegalStateException: could not generate key in keystore android.security.AndroidKeyPairGenerator.generateKeyPair (AndroidKeyPairGenerator.java:99) java.security.KeyPairGenerator$KeyPairGeneratorImpl.generateKeyPair (KeyPairGenerator.java:276) devliving.online.securedpreferencestore.EncryptionManager.generateRSAKeys (EncryptionManager.java:488) devliving.online.securedpreferencestore.EncryptionManager.generateKey (EncryptionManager.java:348) devliving.online.securedpreferencestore.EncryptionManager.<init> (EncryptionManager.java:95) devliving.online.securedpreferencestore.SecuredPreferenceStore.<init> (SecuredPreferenceStore.java:36) devliving.online.securedpreferencestore.SecuredPreferenceStore.getSharedInstance (SecuredPreferenceStore.java:42)

Is there any solutions to this problem?

I'm using minSdk 21 and target 25.
The device info is:-

Manufacturer: Samsung
Model: SHV-E470S
Board: Msm8974
Android API: 21
Android OS: 5.0.1

[iamMehedi]

Most probably due to this issue, which is not supposed to happen on API level >= 21 but here it is!