When creating RSA keys from a PKCS#1 or PKCS#8 encoding that involves OtherPrime information (meaning more than two primes is used to create the modulus), the resulting key is an RSAPrivateKeyImpl. While this works fine and n and d are used during private key operations, it discards the usual CRT components as well as the OtherPrime info, making it impossible to move to another provider that does support multi-prime RSA.

The encoded data from this kind of key then populates zero values for the CRT components and loses all OtherPrime elements.