How to understand why I have random TLS issue on Heroku?

Question

I have calls to my Heroku app using Ruby Net::HTTP

http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
req = Net::HTTP::Post.new(uri.path, { 'Content-Type' => 'application/json' })

Sometimes on those calls I have

SSL_connect returned=1 errno=0 state=SSLv2/v3 read server hello A: tlsv1 alert internal error

This random and on every version of Ruby.

If I run an SSL-Labs test on my domains I have different behavior between dynos. No errors:

White errors:

What can I do? How to better find out what is happening?

PS: I already contacted Heroku support