"umod" returns different data on same input.

[dartedfa]

I'm using node-sshpk Library to sign data with openssh 8.0 generated private key. I have directly imported it in react code. As I have checked it's using browserify-rsa, which has as a dependency bn.js. So I have also checked that, after passing same data to:
return new Buffer(m2.imul(blinds.unblinder).umod(priv.modulus).toArray(false, len));
.umod always returns data randomly it's always different.
Problem occurs only on openssh 8.0 generated private key. keys generated with older version of openssh works as expected.

[dartedfa]

This is a not working key example:

-----BEGIN OPENSSH PRIVATE KEY-----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-----END OPENSSH PRIVATE KEY-----

it doesn't need any passphrase.

Thanks in advance.