If I use an anchored textframe to have abbreviated versions of the headlines as running head, they override every following trigger until the end of the story.

I use character styles as trigger set to 'last on page'.

Please fix this. (Or configure a better way for customizable running headers. Preferable in combination with the table of content)

See also the following post:
https://community.adobe.com/t5/indesign-discussions/indesign-randomly-skipping-text-variable-triggers-for-running-headers/m-p/11700448#M408635