Search result displays all products over 38 pages

When I search for a product, in my case my search query was ‘LM’, it displays a search result page with 5 pages (link). I know I have 29 products containing ‘LM’, but I understand it’s possible to find other products containing ‘LM’ in any shape or form.

But the real problems start when I want to navigate through the resulting pages. Clicking ‘next page’ or any page number in the pagination results in the second page being displayed, but my pagination is increased from 5 to 38(!) (link). It looks like all products are loaded instead of the products initially found by the search query.

I’m also being redirected to the homepage whenever I try to display more products than the initial 12, using the default ‘amount of products per page’ functionality (link).