A while ago there was a known memory leak, and I'm not sure if anyone fixed it, as the developers knew anybody who had a computer capable of running Dolphin well probably had enough RAM for the leak to be a non-issue. The devs like to prioritise the most important or interesting problems, as they're making Dolphin in their free time, so tracking down and eliminating a memory leak probably doesn't appeal to them when there are other things to do.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56