Helm: Helm upgrade fails upgrade ConfigMap

I keep having issues with ConfigMaps not getting updated on helm upgrade. It's not a permanent issue so I can't give an exact scenario how to reproduce. I'll try to give as much info as possible. When I'm saying it's not a permanent issue I mean it doesn't always happen when I'm changing ConfigMaps but when it does happen I can run the upgrade any number of times and the value won't change.

What I'm trying to do

I have a ConfigMap that looks like this. I'm trying to change the value of APP_DOMAIN from test.mydomain.com to develop.europa.mydomain.com.

kubectl describe cm jupiter-config
Name:       jupiter-config
Namespace:  develop
Labels:     <none>
Annotations:    kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"v1","data":{"API_URL":"http://node-services","APP_DOMAIN":"test.mydomain.com","LOG_LEVEL":"info",...

Data
====
SHOW_ADS:
----
true
API_URL:
----
http://node-services
APP_DOMAIN:
----
test.mydomain.com
HTTP_DEBUG:
----
true
LOG_LEVEL:
----
info

I run a helm upgrade to change this value to develop.europa.mydomain.com. You can see the debug output from Helm. The upgrade completes successfully but the ConfigMap stays the same.

helm version output

Client: &version.Version{SemVer:"v2.4.1", GitCommit:"46d9ea82e2c925186e1fc620a8320ce1314cbb02", GitTreeState:"clean"}
Server: &version.Version{SemVer:"v2.4.1", GitCommit:"46d9ea82e2c925186e1fc620a8320ce1314cbb02", GitTreeState:"clean"}

helm upgrade output

REVISION: 61
RELEASED: Tue May 23 15:11:34 2017
CHART: jupiter-0.1.0
USER-SUPPLIED VALUES:
cluster: europa
config:
  API_URL: http://node-services
  APP_DOMAIN: develop.europa.mydomain.com
  HTTP_DEBUG: "true"
  LOG_LEVEL: info
  SHOW_ADS: "true"
resources:
  limits:
    cpu: 500m
    memory: 500Mi
  requests:
    cpu: 100m
    memory: 100Mi
scaling:
  maxReplicas: 4
  minReplicas: 2
version: 1

COMPUTED VALUES:
cluster: europa
config:
  API_URL: http://node-services
  APP_DOMAIN: develop.europa.mydomain.com
  HTTP_DEBUG: "true"
  LOG_LEVEL: info
  SHOW_ADS: "true"
resources:
  limits:
    cpu: 500m
    memory: 500Mi
  requests:
    cpu: 100m
    memory: 100Mi
scaling:
  maxReplicas: 4
  minReplicas: 2
version: 1

HOOKS:
MANIFEST:

---
# Source: jupiter/templates/config.yaml
kind: ConfigMap
apiVersion: v1
metadata:
  name: jupiter-config
data:
  API_URL: http://node-services
  APP_DOMAIN: develop.europa.mydomain.com
  HTTP_DEBUG: "true"
  LOG_LEVEL: info
  SHOW_ADS: "true"