[Gelöst] End slash not showing in hreflang="en" URL

Background of the issue:
I am trying to check the Spanish product page source, but the end slash is not showing for the English URL in the hreflang attribute. The actual English product URL is versteckter Link. The issue can be seen at view-source:versteckter Link.

Symptoms:
The end slash is missing in the hreflang="en" URL. I expected to see versteckter Link but instead got versteckter Link.

Questions:
Why is the end slash missing in the hreflang="en" URL?
How can I ensure the correct URL with the end slash is displayed?