Client-SSL Profile Error: "SSL forward proxy RSA CA key is missing"??

That's the weird thing though - SSL forward proxy is disabled. I'm sending the following payload to the endpoint "https://my.f5.com/mgmt/tm/ltm/profile/client-ssl":

{
    "name": "cssl_my_default",
    "partition": "Common",
    "alertTimeout": "10",
    "allowDynamicRecordSizing": "disabled",
    "allowNonSsl": "disabled",
    "appService": "none",
    "bypassOnClientCertFail": "disabled",
    "bypassOnHandshakeAlert": "disabled",
    "cacheSize": 262144,
    "cacheTimeout": 3600,
    "cert": "/Common/mycrt",
    "certExtensionIncludes": [
        "basic-constraints",
        "subject-alternative-name"
    ],
    "certLifespan": 30,
    "certLookupByIpaddrPort": "disabled",
    "chain": "/Common/entrust_certification_authority_-_l1k",
    "cipherGroup": "none",
    "ciphers": "DEFAULT",
    "defaultsFrom": "/Common/clientssl",
    "description": "::dev:: none",
    "genericAlert": "enabled",
    "handshakeTimeout": "10",
    "inheritCertkeychain": "false",
    "key": "/Common/mykey",
    "maxActiveHandshakes": "indefinite",
    "maxAggregateRenegotiationPerMinute": "indefinite",
    "maxRenegotiationsPerMinute": 5,
    "maximumRecordSize": 16384,
    "modSslMethods": "disabled",
    "mode": "enabled",
    "notifyCertStatusToVirtualServer": "disabled",
    "ocspStapling": "disabled",
    "tmOptions": [
        "dont-insert-empty-fragments"
    ],
    "peerNoRenegotiateTimeout": "10",
    "proxyCaCert": "none",
    "proxyCaKey": "none",
    "proxySsl": "disabled",
    "proxySslPassthrough": "disabled",
    "renegotiateMaxRecordDelay": "indefinite",
    "renegotiatePeriod": "indefinite",
    "renegotiateSize": "indefinite",
    "renegotiation": "enabled",
    "secureRenegotiation": "require",
    "serverName": "none",
    "sessionMirroring": "disabled",
    "sessionTicket": "disabled",
    "sessionTicketTimeout": 0,
    "sniDefault": "false",
    "sniRequire": "false",
    "sslForwardProxy": "disabled",
    "sslForwardProxyBypass": "disabled",
    "sslSignHash": "any",
    "strictResume": "disabled",
    "uncleanShutdown": "enabled"
}