ActiveRecord::RecordInvalid: Validation failed: Payload must be a valid json schema

https://sentry.gitlab.net/gitlab/gitlabcom/issues/2918825/?referrer=gitlab_plugin

ActiveRecord::RecordInvalid: Validation failed: Payload must be a valid json schema
  lib/gitlab/database/load_balancing/connection_proxy.rb:119:in `block in write_using_load_balancer'
    connection.send(...)
  lib/gitlab/database/load_balancing/load_balancer.rb:109:in `block in read_write'
    yield connection
  lib/gitlab/database/load_balancing/load_balancer.rb:176:in `retry_with_backoff'
    return yield
  lib/gitlab/database/load_balancing/load_balancer.rb:107:in `read_write'
    retry_with_backoff do
  lib/gitlab/database/load_balancing/connection_proxy.rb:118:in `write_using_load_balancer'
    @load_balancer.read_write do |connection|
...
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