A little update from my side: There still seem to be some really odd issues, as you said, especially when it comes to Kana imputs.
For example I tried searching for ほうげん and a whole lot of entries showed up, nothing relevant and some that really make me wonder, why they even turned up with that search in the first place. But since I was rather sure that this word should be in the database I tried to search for the Geman translation which did the trick perfectly and just showed mit the entry for ほうげん.
So to make a long story short, the search function is still far from being relaible and I just wanted to let you know and give you a warning - sadly it might still be necessary to double-check your search results. 
I really hope they can get that fixed soon…
Thanks for the update, @neko-chan. 
Your description seems to match my experiences since my last post as well. There are definitely some oddities lingering with the kana search. I was encountering similar things occasionally before all of this, so I’m already pretty accustomed to needing to narrow my searches sometimes with the other fields, but it does seem to be occurring more frequently now.
I’ll usually search by the kanji/English in addition to the kana, unless it gives me a small number of results that contain exactly what I was looking for. Hopefully they’re still tinkering with it (as long as it doesn’t get completely broken again! xD)
Looks like there is a new wrinkle to this long standing database issue. I just uploaded 125 items from an Excel worksheet into a course with 5 levels (one for each of 5 consecutive calendar years of historical dates). The uploading went fine. The items display in consecutive date order in both the levels and the existing database. They seem to test in date order as well (although I haven’t tested all 125 items yet).
The new wrinkle is that the Preview function on each course level is not previewing the items in the order in which it should. There is some kind of disconnect in that underlying logic. It is not really harmful to learning the course, but it is something that should be looked at since it makes it appear that things are not what they should be (chronological order, in my example) and yet they really are. Has anyone else noticed this ? Thanks.
Now that you mention it, I’ve also noticed this, and have actually been encountering it since the issues originally began.
I assumed at the time that it was somehow due to the database entries being in the wrong order, but even now, after the database order’s been fixed, that issue persists.
Same here. I guess it was there all along, we just couldn’t tell. I hope they can fix it. I rely on the Preview function a lot during course creation.
That is a separate bug, and one of the earliest bugs reported on this new forum:
Memrise has not responded to it yet, and the bug is still present of course.
@cos ~ good to know this is nothing new, just something still remaining on the “to do” list for Memrise to fix. Thanks.
the database search is not functioning when ading new items… usually, items already present in my own courses appeared in the drop down menu one sees when adding new items. That is definitely ot showing items from my own database, so, I have to use a separate window to see if the item is already present in my course…