Elastict Tracing "error validating JSON document against schema"

Using traefik 2.4
Elastic Tracing > elastic apm server version 7.6.1

traefik docker command

(...)
- --tracing=true
- --tracing.elastic=true
- --tracing.serviceName=traefik
- --tracing.elastic.serverurl=http://0.0.0.0:9200
- --tracing.elastic.serviceenvironment=dev
(...)

An error log comes up from the elastic apm server, and I can't check the transactions in Kibana.
But can see the metrics.

021-03-17T10:25:44.931Z	ERROR	[request]	middleware/log_middleware.go:95	data validation error	{"request_id": "e4625921-8451-4edf-8d92-2bff1c28ee5c", "method": "POST", "URL": "/intake/v2/events", "content_length": -1, "remote_address": "10.255.202.151", "user-agent": "elasticapm-go/1.7.0 go/go1.15.7", "response_code": 400, "error": "error validating JSON document against schema: I[#] S[#] doesn't validate with \"span#\"\n  I[#] S[#/allOf/3] allOf failed\n    I[#/context/destination/service] S[#/allOf/3/properties/context/properties/destination/properties/service/required] missing properties: \"name\", \"resource\" [{\"span\":{\"duration\":0.073477,\"id\":\"52dda47487cdba5c\",\"name\":\"forward api@internal/api@internal\",\"timestamp\":1615976685911813,\"trace_id\":\"78902112ee7867e906f5043eee940e84\",\"transaction_id\":\"78902112ee7867e9\",\"type\":\"external\",\"context\":{\"destination\":{\"service\":{\"type\":\"external\"}},\"http\":{\"url\":\"http:///api/overview\"},\"tags\":{\"router_name\":\"api@internal\",\"http_host\":\"202.8.174.146:5000\",\"http_status_code\":\"200\",\"span_kind\":\"client\",\"service_name\":\"api@internal\"}},\"parent_id\":\"78902112ee7867e9\",\"stacktrace\":[],\"subtype\":\"http\"}}], error validating JSON document against schema: I[#] S[#] doesn't validate with \"span#\"\n  I[#] S[#/allOf/3] allOf failed\n    I[#/context/destination/service] S[#/allOf/3/properties/context/properties/destination/properties/service/required] missing properties: \"name\", \"resource\" [{\"span\":{\"duration\":0.059737,\"id\":\"b16251f2cba087a4\",\"name\":\"forward api@internal/api@internal\",\"timestamp\":1615976686913825,\"trace_id\":\"a9d4f3c15fe8efb7bbaaa547bc0d1467\",\"transaction_id\":\"a9d4f3c15fe8efb7\",\"type\":\"external\",\"context\":{\"destination\":{\"service\":{\"type\":\"external\"}},\"http\":{\"url\":\"http:///api/overview\"},\"tags\":{\"router_name\":\"api@internal\",\"http_host\":\"202.8.174.146:5000\",\"http_status_code\":\"200\",\"span_kind\":\"client\",\"service_name\":\"api@internal\"}},\"parent_id\":\"a9d4f3c15fe8efb7\",\"stacktrace\":[],\"subtype\":\"http\"}}], error validating JSON document against schema: I[#] S[#] doesn't validate with \"span#\"\n  I[#] S[#/allOf/3] allOf failed\n    I[#/context/destination/service] S[#/allOf/3/properties/context/properties/destination/properties/service/required] missing properties: \"name\", \"resource\" [{\"span\":{\"duration\":0.063531,\"id\":\"a7f2c725b479f6d1\",\"name\":\"forward api@internal/api@internal\",\"timestamp\":1615976690910623,\"trace_id\":\"d4fa27b4d7efed42abc53680bef97e49\",\"transaction_id\":\"d4fa27b4d7efed42\",\"type\":\"external\",\"context\":{\"destination\":{\"service\":{\"type\":\"external\"}},\"http\":{\"url\":\"http:///api/overview\"},\"tags\":{\"http_host\":\"202.8.174.146:5000\",\"http_status_code\":\"200\",\"span_kind\":\"client\",\"service_name\":\"api@internal\",\"router_name\":\"api@internal\"}},\"parent_id\":\"d4fa27b4d7efed42\",\"stacktrace\":[],\"subtype\":\"http\"}}], error validating JSON document against schema: I[#] S[#] doesn't validate with \"span#\"\n  I[#] S[#/allOf/3] allOf failed\n    I[#/context/destination/service] S[#/allOf/3/properties/context/properties/destination/properties/service/required] missing properties: \"name\", \"resource\" [{\"span\":{\"duration\":0.098104,\"id\":\"396c7c76ee9d47a8\",\"name\":\"forward api@internal/api@internal\",\"timestamp\":1615976691971999,\"trace_id\":\"5d54889150c96d65985ec6534a042e9a\",\"transaction_id\":\"5d54889150c96d65\",\"type\":\"external\",\"context\":{\"destination\":{\"service\":{\"type\":\"external\"}},\"http\":{\"url\":\"http:///api/overview\"},\"tags\":{\"router_name\":\"api@internal\",\"http_host\":\"202.8.174.146:5000\",\"http_status_code\":\"200\",\"span_kind\":\"client\",\"service_name\":\"api@internal\"}},\"parent_id\":\"5d54889150c96d65\",\"stacktrace\":[],\"subtype\":\"http\"}}], error validating JSON document against schema: I[#] S[#] doesn't validate with \"span#\"\n  I[#] S[#/allOf/3] allOf failed\n    I[#/context/destination/service] S[#/allOf/3/properties/context/properties/destination/properties/service/required] missing properties: \"name\", \"resource\" [{\"span\":{\"duration\":0.092409,\"id\":\"c780b9d75acb1b27\",\"name\":\"forward api@internal/api@internal\",\"timestamp\":1615976695911088,\"trace_id\":\"026714f1afa0c57f9c73e67b984a0132\",\"transaction_id\":\"026714f1afa0c57f\",\"type\":\"external\",\"context\":{\"destination\":{\"service\":{\"type\":\"external\"}},\"http\":{\"url\":\"http:///api/overview\"},\"tags\":{\"router_name\":\"api@internal\",\"http_host\":\"202.8.174.146:5000\",\"http_status_code\":\"200\",\"span_kind\":\"client\",\"service_name\":\"api@internal\"}},\"parent_id\":\"026714f1afa0c57f\",\"stacktrace\":[],\"subtype\":\"http\"}}]"}


May I know what the problem is?