diff --git a/src/realtime/MCWSEVRLevelStreamProvider.js b/src/realtime/MCWSEVRLevelStreamProvider.js
index 7f90918..60aa9c9 100644
--- a/src/realtime/MCWSEVRLevelStreamProvider.js
+++ b/src/realtime/MCWSEVRLevelStreamProvider.js
@@ -31,7 +31,9 @@ class MCWSEVRLevelStreamProvider extends MCWSStreamProvider {
    * @returns {String} The key
    */
   getKey(domainObject) {
-    return domainObject.telemetry.level;
+    // only uppercase works for all mcws apis (lowercase will not work)
+    // see https://github.com/NASA-AMMOS/openmct-mcws/pull/412/changes
+    return domainObject.telemetry.level.toUpperCase();
   }
 }
 
diff --git a/src/realtime/MCWSEVRStreamProvider.js b/src/realtime/MCWSEVRStreamProvider.js
index b0d1b06..6e4fed4 100644
--- a/src/realtime/MCWSEVRStreamProvider.js
+++ b/src/realtime/MCWSEVRStreamProvider.js
@@ -32,20 +32,29 @@ class MCWSEVRStreamProvider extends MCWSStreamProvider {
    */
   getKey(domainObject) {
     // Can subscribe only by EVR module even if subscribing by EVR
-    let module =
-      domainObject.telemetry &&
-      domainObject.telemetry.definition &&
-      domainObject.telemetry.definition.module &&
-      domainObject.telemetry.definition.module.toLowerCase();
+    // This is the default cause for EVRs that contain a module.
+    // only uppercase works for all mcws apis (lowercase will not work)
+    // see https://github.com/NASA-AMMOS/openmct-mcws/pull/412/changes
+    let module = domainObject?.telemetry?.definition?.module?.toUpperCase();
+
+    // This is the top-level vista.evrModule object, which contains
+    // a module definition but not in the definition object.
+    // This must be captured before attempting legacy EVRs,
+    // in case the module contains underscores.
+    // only uppercase works for all mcws apis (lowercase will not work)
+    // see https://github.com/NASA-AMMOS/openmct-mcws/pull/412/changes
+    if (!module?.length) {
+        module = domainObject?.telemetry?.module?.toUpperCase();
+    }
 
     // legacy inference of module by evr_name
-    // if this fallback is used will break on module names containing underscores
+    // This should *never* occur with modern telemetry dictionaries.
     if (!module || module.length <= 0) {
       console.warn('Legacy domain objects should not be used anymore!');
-      module = domainObject.telemetry.evr_name
-        ? domainObject.telemetry.evr_name.split('_')[0].toLowerCase()
-        : domainObject.telemetry.module.toLowerCase();
-    }
+      // only uppercase works for all mcws apis (lowercase will not work)
+      // see https://github.com/NASA-AMMOS/openmct-mcws/pull/412/changes
+      module = domainObject.telemetry.evr_name.split('_')[0].toUpperCase();
+  }
 
     return module;
   }
diff --git a/src/realtime/MCWSStreamWorkerScript.js b/src/realtime/MCWSStreamWorkerScript.js
index 7824a27..3315614 100644
--- a/src/realtime/MCWSStreamWorkerScript.js
+++ b/src/realtime/MCWSStreamWorkerScript.js
@@ -212,7 +212,9 @@
         const data = JSON.parse(message.data);
 
         data.forEach((datum) => {
-          const key = datum[property];
+          // only uppercase works for all mcws apis (lowercase will not work)
+          // see https://github.com/NASA-AMMOS/openmct-mcws/pull/412/changes
+          const key = datum[property].toUpperCase();
 
           if (subscribers[key] > 0) {
             self.postMessage({