Kubernetes 1.4.7, Helm/Tiller v2.1.3

I have a strange behavior from helm upgrade (v2.1.3) here. I've changed environment variables of a charts template (deployment) but those env's don't get updated by helm upgrade.
helm get shows the correctly updated manifest but in kubectl get deployment -o yaml the variables are missing. I'm able to kubectl apply the manifest I get from helm get without errors.

Installing a new release uses the correct env variables though.

Sadly I don't know how to this can be reproduced. Installing a new release and changing variables there works okay but the already broken releases stay broken.

I'm happy to dig deeper into this - unfortunately I don't know much about how to debug tiller.

Users on slack report similar problems.

/cc @thomastaylor312