Several users report that sometimes opening the Visual Editor gets stuck, caused by the browser failing to load the script https://fr.wikipedia.org/w/load.php?debug=false&lang=fr&modules=diffMatchPatch%2Cmoment%2Coojs-ui%2Coojs-ui-core%2Coojs-ui-toolbars%2Coojs-ui-widgets%2Coojs-ui-windows%2Cpapaparse%2Crangefix%2Cspark-md5%2CtreeDiffer%2Cunicodejs%7Cext.CodeMirror.data%2Clib%2CvisualEditor%7Cext.CodeMirror.mode.mediawiki%7Cext.CodeMirror.visualEditor.init%7Cext.abuseFilter.visualEditor%7Cext.cite.style%2CvisualEditor%7Cext.cite.visualEditor.core%2Cdata%2Cicons%7Cext.citoid.visualEditor%7Cext.citoid.visualEditor.data%7Cext.confirmEdit.visualEditor%7Cext.disambiguator.visualEditor%7Cext.geshi.visualEditor%7Cext.graph.data%2CvisualEditor%7Cext.kartographer%7Cext.kartographer.editing%2Cutil%2CvisualEditor%7Cext.math.styles%2CvisualEditor%7Cext.math.visualEditor.icons%7Cext.score.visualEditor%7Cext.score.visualEditor.icons%7Cext.spamBlacklist.visualEditor%7Cext.templateDataGenerator.editPage%7Cext.titleblacklist.visualEditor%7Cext.visualEditor.articleTarget%2Cbase%2Ccore%2Cdata%2CdesktopArticleTarget%2CdesktopTarget%2Cdiffing%2Cicons%2Clanguage%2Cmediawiki%2CmoduleIcons%2CmoduleIndicators%2Cmwalienextension%2Cmwcore%2Cmwextensionmessages%2Cmwextensions%2Cmwformatting%2Cmwgallery%2Cmwimage%2Cmwlanguage%2Cmwlink%2Cmwmeta%2Cmwsave%2Cmwsignature%2Cmwtransclusion%2Cmwwikitext%2Cswitching%2Cwelcome%7Cext.visualEditor.core.desktop%7Cext.visualEditor.mwextensions.desktop%7Cext.visualEditor.mwimage.core%7Cext.wikihiero.visualEditor%7Cext.wikimediaEvents.visualEditor%7Cjquery.lengthLimit%7Cmediawiki.ForeignStructuredUpload%2CForeignUpload%2CUpload%2Cwidgets%7Cmediawiki.ForeignStructuredUpload.BookletLayout%2Cconfig%7Cmediawiki.Upload.BookletLayout%7Cmediawiki.action.view.redirectPage%7Cmediawiki.diff.styles%7Cmediawiki.language.names%7Cmediawiki.libs.jpegmeta%7Cmediawiki.page.gallery.styles%7Cmediawiki.skinning.content.parsoid%7Cmediawiki.widgets.AbandonEditDialog%2CCategoryMultiselectWidget%2CDateInputWidget%2CMediaSearch%2CStashedFileWidget%2CUserInputWidget%2Cstyles%7Cmediawiki.widgets.DateInputWidget.styles%7Coojs-ui-core.styles%7Coojs-ui.styles.icons-accessibility%2Cicons-alerts%2Cicons-content%2Cicons-editing-advanced%2Cicons-editing-citation%2Cicons-editing-core%2Cicons-editing-list%2Cicons-editing-styling%2Cicons-interactions%2Cicons-layout%2Cicons-location%2Cicons-media%2Cicons-moderation%2Cicons-movement%2Cicons-user%2Cicons-wikimedia%2Cindicators%2Ctextures&skin=vector&version=0kf882p (or something with a similar URL).
The reported error in Chrome is net::ERR_SPDY_PROTOCOL_ERROR 200, in Firefox (where the error occurs more frequently, probably due to the fact that in Firefox MW doesn't use localStorage as additional cache) the error is Loading failed for the <script> with source ...
See T214534#4923429 for a HAR log, though a comment on stackoverflow with very similar symptoms suggests that the issue is not on the client side, but with nginx or some other proxy.
Original report:
Noticed now here: https://pt.wikipedia.org/wiki/P%C3%AAro_Dias?veaction=edit , but I've been seeing this behaviour for some time already.