It turns out in the code excerpt I wrote to demonstrate my problem, the problem is easily solved by setting 'keep_encoding => 1' when the Twig is created.

In the actual code that is trying to do this same thing, 'keep_encoding => 1' is set but the output behaves like it is not set. And I get the behavior described in the original message. Maybe this additional information will ring a bell with someone.

It's hard to help when the code you post doesn't reflect the actual problem you're experiencing. If you can, post an example that behaves improperly with the undesired output as well as the desired output.