[Theme: Twenty Fourteen] Content of ephemera widgets show single post meta data

Hello,

when showing a single post the emphemera widgets in the left sidebar all show the same meta data (date, link, link name, comments…). It is the data from the single post shown on this page.

See here:
https://www.sebald.com/2014/02/01/guillaume-nery-base-jumping-deans-blue-hole/

Everything works when a category page or something like this is shown.

I know that something gets between things, most likely a plugin, and messes with some variables or something like this.

Could you help my dig into it? I already deactivated most plugins but the single post page did not change.

Thanks and cheers,
Martin