After disabling Diffie-Hellman and GCM ciphers the TIM SSL Server Status page still shows many unsupported cipher suite decode failures and TIM logs also show unsupported ECDH and AES GCM ciphers i.e.
"CipherSuite - Unknown (49171)" = TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
"CipherSuite - Unknown (156)" = TLS_RSA_WITH_AES_128_GCM_SHA256
The web server has this SSLCipherSuite setting:
Diffie-Hellman and GCM ciphers have several different classifications e.g. DH, ADH, EDH, ECDH and GCM, AESGCM. They all need to be disabled to force the web server to use a cipher suite that is supported by the TIM.
This final setting for SSLCipherSuite was successful in disabling all Diffie-Hellman & GCM ciphers
After restarting the TIM the refreshed TIM SSL Server Status page then showed valid connections with no decode failures for unsupported cipher suites.
The TIM logs also reported that this supported cipher was being used: TLS_RSA_WITH_AES_256_CBC_SHA (53)