Yes, rebuild command and also initiated upgrade from GUI gave the same error.
Retrying fetcher due to error (4/4): Bundler::HTTPError Could not fetch specs from https://rubygems.org/ due to underlying error <Net::OpenTimeout: execution expired (https://rubygems.org/specs.4.8.gz)>
There was an error installing the locked bundler version (2.4.4), rerun with the `--verbose` flag for more details. Going on using bundler 2.3.6.
Fetching source index from https://rubygems.org/
Could not fetch specs from https://rubygems.org/ due to underlying error
<Net::OpenTimeout: execution expired (https://rubygems.org/specs.4.8.gz)>
Docker Manager: FAILED TO UPGRADE