Go with the washer (or at least try it first!). It’s simple and cheap.
As pointed out in the video link above, the filter assembly has a tiny "wedge" that must be fully pressed in for the filter system to work. It seems that new filters, even official brand ones, do not fully press this "wedge".
We bought garden hose washers at home improvement store. Make sure the inner cut-out is wide enough to go around the nozzle in the filter assembly.
One final comment: We bought rubber garden hose washers because it seemed like rubber was "better" than metal. However, after a week of the filter working, the noise and lack of water pressure returned. Upon removing the filter, it was clear that the little "wedge" had actually made an indent into the rubber washer. So I think a metal washer (possibly combined with a rubber washer) may be the real way to go. So a thin metal + rubber washer would probably be the best or just a single reasonable width metal washer or a hard plastic washer.
Check out the “slight” indent in the first rubber washer. It was much more pronounced right after removing it from the filter assembly (picture taken about 4 days after we switched it). We fixed the filter again by using another of the 10 rubber filters we bought but I’m willing to be in another week or so, we’ll have to either swap that one out with another “new” rubber one (or rotate or flip the one currently in the filter assembly). Hence, my suggestion to use a metal or “very hard” rubber one.
Thanks to @shrinivas for the easy and cheap fix!