Half flushes are like the decaf coffee of the toilet world—sounds good in theory, but sometimes just doesn’t do the job. I’ve run into this a lot, especially with older plumbing or certain brands that just seem to have weak sauce half-flushes no matter what you tweak. Once, I spent an hour fiddling with a dual-flush at my aunt’s place, only to realize the internal mechanism was just... cheap. Sometimes it really is the design, not you or your pipes. If you’ve checked for buildup and adjusted everything, it might just be one of those “it is what it is” situations. Not all toilets are created equal, unfortunately.
Yeah, I’ve noticed the same thing with some dual-flush models—half flush just isn’t enough, especially for anything more than a bit of tissue. Have you checked if the water level in the tank is set high enough? Sometimes adjusting that float can help, but honestly, with certain brands it barely makes a difference. I’ve swapped out a few for tenants over the years just because the half flush was more of a suggestion than an actual function. Some designs just don’t cut it, no matter what you do.