When I try to edit page (on labs, as of 06 august 2017) using 2017 editor, it does not end loading (progress bar stops). It shows errors releated to codemirror, even I disable this in preferences (this may be additional issue).
TypeError: mwConfig is null mediawiki.js:26:4 <anonymous> https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/mode/mediawiki/mediawiki.js:26:4 getMode https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/lib/codemirror/lib/codemirror.js:1439:17 loadMode https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/lib/codemirror/lib/codemirror.js:4464:17 attachDoc https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/lib/codemirror/lib/codemirror.js:4562:3 CodeMirror$1 https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/lib/codemirror/lib/codemirror.js:7436:3 CodeMirror$1 https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/lib/codemirror/lib/codemirror.js:7389:49 ve.ui.CodeMirrorAction.prototype.toggle https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/modules/ve-cm/ve.ui.CodeMirrorAction.js:46:20 ve.ui.Surface.prototype.execute https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/lib/ve/src/ui/ve.ui.Surface.js:691:10 ve.ui.Command.prototype.execute https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/lib/ve/src/ui/ve.ui.Command.js:40:10 ve.ui.CodeMirrorTool.prototype.onSurfaceChange https://en.wikipedia.beta.wmflabs.org/w/extensions/CodeMirror/resources/modules/ve-cm/ve.ui.CodeMirrorTool.js:61:3 oo.EventEmitter.prototype.emit https://en.wikipedia.beta.wmflabs.org/w/resources/lib/oojs/oojs.jquery.js:829:5 ve.ui.Toolbar.prototype.setup https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/lib/ve/src/ui/ve.ui.Toolbar.js:76:3 ve.init.Target.prototype.setupToolbar https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/lib/ve/src/init/ve.init.Target.js:519:2 ve.init.mw.ArticleTarget.prototype.setupToolbar https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/modules/ve-mw/init/ve.init.mw.ArticleTarget.js:1813:2 ve.init.mw.DesktopArticleTarget.prototype.setupToolbar https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/modules/ve-mw/init/targets/ve.init.mw.DesktopArticleTarget.js:256:2 ve.init.Target.prototype.setSurface https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/lib/ve/src/init/ve.init.Target.js:469:3 ve.init.mw.Target.prototype.setSurface https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/modules/ve-mw/init/ve.init.mw.Target.js:408:2 ve.init.mw.DesktopArticleTarget.prototype.setSurface https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/modules/ve-mw/init/targets/ve.init.mw.DesktopArticleTarget.js:494:2 ve.init.mw.Target.prototype.setupSurface/</< https://en.wikipedia.beta.wmflabs.org/w/extensions/VisualEditor/modules/ve-mw/init/ve.init.mw.Target.js:381:4