@danlyke
Ah. My curiosity thanks you profusely. 😎
@ClaraListensprechen4 grin. Yeah, the kind of answers that source best from other users ("put a quarter in the bottom of the filter holder and reassemble. If that fixes it, then..."), that already sent me down the wrong road of fixing (I also had a faulty water pressure test gauge that lied to me, and jumped through those hoops), and that if the manufacturer had provided useful results I wouldn't have had the problem...
@ClaraListensprechen4 Aquasana water filter (apparently there was a batch of filter cores that were too short, causing an automated shut off to partially kick in, resulting in super slow fill rates. Solution is a nylon washer as a spacer.)
Toto Bidet (figuring out how to get the water filter cartridge out. Which was easy and obvious, but I needed the confidence of "yes that's it, twist it harder".)