Azure.Diagnostics.LinuxDiagnostic "Failed to set up mdsd dependencies"

i`m getting an error from:
TYPE Microsoft.Azure.Diagnostics.LinuxDiagnostic
VERSION 3.0.117

OS:
Ubuntu 16.04 (x86_64) | 16.04.201808140

Other extensions present related to this (successfully installed):

DependencyAgentLinux: VERSION 9.7.3.1475
OmsAgentForLinux: VERSION 1.8.9

Error message:
Failed to set up mdsd dependencies: omsagent setup failed 5 times. Last exit code=3, Output=setup_omsagent_for_lad(): fluentd out_mdsd plugin install failed. Output: /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- rubygems/safe_yaml (LoadError) from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems.rb:702:in `load_yaml' from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/config_file.rb:340:in `load_file' from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/config_file.rb:202:in `initialize' from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/gem_runner.rb:75:in `new' from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/gem_runner.rb:75:in `do_configuration' from /opt/microsoft/omsagent/ruby/lib/ruby/2.4.0/rubygems/gem_runner.rb:40:in `run' from /opt/microsoft/omsagent/ruby/lib/ruby/gems/2.4.0/gems/fluentd-0.12.40/bin/fluent-gem:6:in `' from /opt/microsoft/omsagent/ruby/bin/fluent-gem:23:in `load' from /opt/microsoft/omsagent/ruby/bin/fluent-gem:23:in `'
HANDLER STATUSReady
HANDLER STATUS LEVELInfo

i could find a similar issue but seems to be closed...
https://github.com/Azure/azure-linux-extensions/issues/488#issuecomment-439878427

Start with Azure.Diagnostics.LinuxDiagnostic version 3.0.117 on Ubuntu 16.04 and trace the reported setup failure through the OmsAgent and fluent-gem paths under /opt/microsoft/omsagent/ruby. Compare the linked issue and verify the missing rubygems/safe_yaml dependency during fluentd plugin installation; done means the extension installs without the mdsd dependency error.

Written by the indexing model from the issue text.