The issue is not specific to enwiki beta - enwiki wmf.26 - https://en.wikipedia.org/wiki/Latrodectism?shareHighlight=1 displays the issue.

The issue is found on enwiki beta and might be specific to beta cluster env

Steps to replicate the issue :

• go to https://en.wikipedia.beta.wmcloud.org/wiki/Polar_bear?shareHighlight=1 (another example Brown_bear)
• as the page loads, the Console immediately shows the following error:

TypeError: parsedUrl.resizeUrl is not a function
    at getImageSrc (ShareQuoteDialog.vue:103:22)
    at tV.eval [as fn] (ShareQuoteDialog.vue:116:13)
    at eR (vue.js:5:8449)
    at get value (vue.js:5:19431)
    at ek.l [as fn] (vue.js:5:55236)
    at ek.run (vue.js:5:6967)
    at k (vue.js:5:55721)
    at vue.js:5:56056
    at rX (vue.js:5:56165)
    at e.watch (vue.js:9:14814)

• the "Share quote" button appears - click on the button

What happens?:

• the "Share quote" button disappears without showing the Share card

What should have happened instead?:

• fix the error so that the dialog is able to load as intended, or
• automatically close the share dialog if the error is not fixable/recoverable

NOTE: there are articles that have no problems displaying a share card with images, e.g. Antarctica