Interesting. We have the same version of FF. (I downloaded the latest V81 this morning). Must be down to different parameter settings. These are my ssl3 & tls settings:
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security.ssl3.dhe_rsa_aes_128_sha false
security.ssl3.dhe_rsa_aes_256_sha false
security.ssl3.ecdhe_ecdsa_aes_128_gcm_sha256 true
security.ssl3.ecdhe_ecdsa_aes_128_sha true
security.ssl3.ecdhe_ecdsa_aes_256_gcm_sha384 true
security.ssl3.ecdhe_ecdsa_aes_256_sha true
security.ssl3.ecdhe_ecdsa_chacha20_poly1305_sha256 true
security.ssl3.ecdhe_rsa_aes_128_gcm_sha256 true
security.ssl3.ecdhe_rsa_aes_128_sha true
security.ssl3.ecdhe_rsa_aes_256_gcm_sha384 true
security.ssl3.ecdhe_rsa_aes_256_sha true
security.ssl3.ecdhe_rsa_chacha20_poly1305_sha256 true
security.ssl3.rsa_aes_128_gcm_sha256 true
security.ssl3.rsa_aes_128_sha true
security.ssl3.rsa_aes_256_gcm_sha384 true
security.ssl3.rsa_aes_256_sha true
security.ssl3.rsa_des_ede3_sha true
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gl.use-tls-is-current 0
media.peerconnection.dtls.version.max 771
media.peerconnection.dtls.version.min 770
network.http.spdy.enforce-tls-profile true
network.http.tls-handshake-timeout 30
network.proxy.proxy_over_tls true
security.tls.enable_0rtt_data true
security.tls.enable_delegated_credentials false
security.tls.enable_post_handshake_auth false
security.tls.hello_downgrade_check true
security.tls.insecure_fallback_hosts
www.crosswordclub.co.uk
security.tls.version.enable-deprecated false
security.tls.version.fallback-limit 4
security.tls.version.max 4
security.tls.version.min 3