Actually, I take it back, I did the 1 connection wrong.. Doing the connection directly didn't trigger the problem.
Thanks Luis, your suggestion made me close the scope in the issue! It was actually a cache done by default by Ecto (Elixir's database library), I just created an issue in Ecto's github https://github.com/elixir-ecto/ecto/issues/3284 and got the response confirming it and also the fix to disable it.