@toggledbits Below, the error and a screenshot while creating a new Global Expression, named "test". Hoping this helps answer your questions.
As soon as I am done typing "test" and clicking in the field to add my formula, the error pops-up and will continue popping-up three times by the time it saved the changes. The error will also pop-up when I delete the expression and will pop-up a second time by the time it saved the changes.
It did not happen on the first use of the tab/function. It took a few tries before I could re-produce the error. It does resolve itself after a page refresh.
@http://192.168.0.13:8111/reactor/en-ca/lib/js/reaction-editor.js:543:91
makeExprMenu@http://192.168.0.13:8111/reactor/en-ca/lib/js/reaction-editor.js:537:28
@http://192.168.0.13:8111/reactor/en-ca/lib/js/reaction-editor.js:92:64
@http://192.168.0.13:8111/reactor/en-ca/lib/js/reaction-editor.js:89:68
each@http://192.168.0.13:8111/node_modules/jquery/dist/jquery.min.js:2:3133
@http://192.168.0.13:8111/reactor/en-ca/lib/js/reaction-editor.js:89:35
@http://192.168.0.13:8111/client/MessageBus.js:98:44
forEach@[native code]
@http://192.168.0.13:8111/client/MessageBus.js:95:54
@http://192.168.0.13:8111/client/MessageBus.js:106:44
@http://192.168.0.13:8111/client/Observable.js:78:28
signalModified@http://192.168.0.13:8111/reactor/en-ca/lib/js/ee.js:146:21
signalModified@http://192.168.0.13:8111/reactor/en-ca/lib/js/expression-editor.js:40:29
reindexExpressions@http://192.168.0.13:8111/reactor/en-ca/lib/js/expression-editor.js:71:32
@http://192.168.0.13:8111/reactor/en-ca/lib/js/expression-editor.js:608:40
dispatch@http://192.168.0.13:8111/node_modules/jquery/dist/jquery.min.js:2:40040