That's interesting, I've seen it happening randomly that a search query would return unrelated results for 1 out of 100 queries using the same query.
In your example however, it seems to me that if you add quotes, the irrelevant results are gone: https://www.ebay.co.uk/sch/i.html?_nkw=%22Tasmota%22
Why are some sellers having all their listings (car parts) included in my search for "Tasmota"?