I have noticed that in the past if you have an item for sale on ebay with various keywords set the item would appear in search no matter how few keywords were used when searching for the item .. but there is a now a problem:

Say for example you have an item called:

"pentax 50mm f2 lens" ..

in the past this would have showed in search results when you searched for "lens" .. now there is no guarantee it will show in any search where you search/filter for "lens" .. to have a better chance of finding that lens you will now need 2 of the keywords .. eg "pentax lens" may be required to have that item show in search .. it all depends how many items are in that "search" .. so if there are lots of "pentax lens" results your item may still not appear in search .. but if you search for "pentax 50mm lens" or "pentax f2 lens" then it will probably appear .. and yes it is a major problem for many many ebay sellers now .. depending on things  like "item specifics", dashboard status, how new or old your selling account is .. best match default standing and probably what subscriptions you have or which ebay promotions you are using (eg ebay plus etc) .. even something vague like postage method (express or regular) or handling times comes into it, business account or personal? etc .. to to put it simply: it is now a lot harder for buyers to find your stuff .. tempted to use ebay promotions now are we? ..

this could be the least of our problems as "they" are still mucking around with the glitchy ebay selling console (which changes in behaviour by the day or minute to minute) (yet we still can not verify our phone numbers??!! plus a whole heap of other problems) and obviously "they" are not finished tweaking cassinni yet (15+ years later) .. anyway suffice to say that cassinni is heavily rigged to favour the well-heeled/connected and "little" to do with "best match" .. cassinni and best match default is a confusing and corrupt "hot mess" that has single handedly decimated ebay yet "they" persist with it ..

marketing 101 of all multinational monopoly practices businesses dictates that marketing credentials trumps common sense .. anyway I haven't got the energy to report the bugs and logic errors any more .. just go to "chat" when money is "missing" following one of their glitches now .. which I have to do again now as got caught up in the ebay voucher/credit card glitch which immediately cancels you ebay purchase after credit card payment while using an ebay voucher (They insisted that I use a credit card to get the voucher .. I feel so used) .. and then ebay holds onto your credit card money (for how long? .. has been a week now) .. maybe one day ebay will get their ducks in a row or collapse .. the way it is looking right now I lean towards the later theory .. this is probably what happens when all/most of your coding is outsourced to "shelf company" contractors based in tax havens who outsource to sub-contractors in the third world who do not speak the same language etc .. creative accountancy will only get you so far ..

as for the OP .. I am not sure how I could advise them .. it would seem that dumping the anchor store would be the solution (right now) but will probably make the search visibility problem worse for them too .. all depending on how cassinni has been rejiggered this week/month etc .. it kinda gets back to selling down inventory whilst the sales are declining and not tooling up for a declining market .. until ebay can breathe vitality back into this steaming mess I am thinking many lesser heeled ebay clientele will see less sales due to their item visibility "rating" in search .. and no it is not just best match default it is not appearing in .. all searches, recently listed. ending soon, lowest price etc etc .. up till this happened ebay was "decreeing" a lot of my stuff is/as "irrelevant" and hiding it in the irrelevant link but now much is hidden completely unless specifically searched for with multiple keywords I used in my item listings heading or item specifics or if customers browse my other listings and find it that way  .. unless using multiple keywords in search etc etc ..

hope that all made sense ..