This issue is resolved in The Bat! v9.1.16. Download page: https://www.ritlabs.com/en/products/thebat/download.php
In an ECDSA signature, if a hash function had larger digest length (in bits) than the field size (which is not a good practice), The Bat! treated these signatures as invalid. It might lead to invalid ECC certificates, e.g. signed by "sha512ECDSA" algorithm. It might also lead to the following error: "TLS protocol error: Internal error BuildClientKeyExchange".