When performing a search instead of results I get:

SearchApiException: Cannot sort on field field_product:commerce_price:amount_decimal of a list type. in SearchApiDbService->search() (line 872 of <snip>/commerce_kickstart/profiles/commerce_kickstart/modules/contrib/search_api_db/service.inc).

I'm new to working with search and did alter some settings a couple of weeks ago so I'm guessing it's related to that, where should I start looking for the cause or, how can I get back to the original settings without losing the rest of the work done since?

Many thanks!