I have found a few issues and since you gave me FTP access, I have implemented an experimental feature, which I plan to add in the upcoming version for more precise results when using the index table.
Issue 1: On the index table options panel, by default common words and words below the length of 3 are not indexed. Therefore the “Go” on the title was never picked up, since it was a common word and below 3 length. I have changed that and created a new index: https://i.imgur.com/7QBdd7z.png
Issue 2: The relevance of the title words was equal to terms and content words. So matches within the content were outweighing the title matches, giving a feeling of less relevant results. I have changed that a little bit: https://i.imgur.com/YkkpbBh.png
Issue 3: The custom ajax handler was actually slower in your case, so I have changed that back on the Compatibility Options panel.
+ Additon: I've changed the index table handler file, which now treats semi-exact title matches with high relevance. Therefore searching for example “BRITAX Kinderwagen Go” will more likely give you products starting with that search phrase. This feature is still under testing, but it should give you much more relevant results.Best,
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