Re: i2d_X509_REQ() -> d2i_X509_REQ() = asn1 encoding routines:c2i_ASN1_OBJECT:invalid object encoding:a_object.c:287

["Salz, Rich via openssl-users" <openssl-users@xxxxxxxxxxx>]

>    This software however is 7 years old, we’re not in a position to drop everything and rewrite it.
  

Then don't upgrade?  If it's for a CA you don't need TLS 1.3 for example.

Or take the existing OpenSSL code that works and jam it into the current release.