Considering IE 11 has Grade A support, and multiple people have been able to replicate this issue, this is probably Unbreak now! priority.

Reported on enwiki also.

Are there any errors in the "Console" or "Network" tab of the Developer Tools? See https://docs.microsoft.com/en-us/microsoft-edge/devtools-guide/console

yes.

jQuery.Deferred exception: Das Objekt unterstützt die Eigenschaft oder Methode "find" nicht
TypeError: Das Objekt unterstützt die Eigenschaft oder Methode "find" nicht
at MMVP.loadImageByTitle (https://de.wikipedia.org/w/load.php?debug=false&lang=de&modules=mmv&skin=vector&version=0n1zvob:102:613)

method find not supported.

Obviously from Replace jQuery by native JavaScript by https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/MultimediaViewer/+/459423/2/resources/mmv/mmv.js line 406

Inner comment: Array.prototype.find is ES6. This change breaks support for older browser that support only ES5: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find#Browser_compatibility

patch-patched by https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/MultimediaViewer/+/460427/1/resources/mmv/mmv.js but not deployed.

@Fomafix

Change 460427 had a related patch set uploaded (by MGChecker; owner: Fomafix):
[mediawiki/extensions/MultimediaViewer@master] Use a for loop instead of Array.prototype.find

https://gerrit.wikimedia.org/r/460427

Change 462150 had a related patch set uploaded (by Krinkle; owner: Fomafix):
[mediawiki/extensions/MultimediaViewer@wmf/1.32.0-wmf.22] Use a for loop instead of Array.prototype.find

https://gerrit.wikimedia.org/r/462150

Change 460427 merged by jenkins-bot:
[mediawiki/extensions/MultimediaViewer@master] Use a for loop instead of Array.prototype.find

https://gerrit.wikimedia.org/r/460427

Change 462150 merged by jenkins-bot:
[mediawiki/extensions/MultimediaViewer@wmf/1.32.0-wmf.22] Use a for loop instead of Array.prototype.find

https://gerrit.wikimedia.org/r/462150

Mentioned in SAL (#wikimedia-operations) [2018-09-22T18:28:59Z] <krinkle@deploy1001> Synchronized php-1.32.0-wmf.22/extensions/MultimediaViewer/resources/: I0954c42a37668b0, T205162 (duration: 00m 56s)