Logging in is definitely good advice for anyone running into issues while logged out. Another thing you could try even if you are logged in: from My View, click on "Recently Modified" and start your search from there. Search settings are saved per-account, so if you've ever performed a search on a weird field, that will persist until you reset it and might not be obvious. "Recently Modified" doesn't reset your search settings, but gives you a clean set of filters you can use to base a new search on (which will overwrite your search settings once it's performed).
The thing is, most of us use the bug tracker regularly. We can see when something we do every single time stops working. And yet continues to work when using a different device.
Process:
My view, click Recently Modified.
Search "Fish". List of results not at all containing the word fish.
Back to my view, click on Recently modified
Search for any other word at all: Exact same results as searching for "fish".
Notable weirdness:
The hide status which was set at "none" when I made the search has changed to "closed (and above)" indicating that this is just some page I once brought up in a search that has "stuck" somehow. And "sticky issues" which I don't recall ever using before has changed to yes.
Back to my view, click on Recently modified.
Clicking "advanced filters" brings up exact same result as searching for "fish".
Back to my view, click on Recently modified.
Clicking "reset filter" brings up the exact same results as searching for "fish".
Again, works fine on my PC. Not on my phone (both Chrome). Stopped happening once before when I cleared my cache. But it's started up again just a short while later and clearing my cache doesn't seem to fix it any more.
Recently modified > View Issues also brings up the exact same list. Most recent entry in that list in April 6th. So none of the more recent bugs are in that list.