I love Signal and use it as much as I can, but I'm thinking of switching to Matrix solely because the desktop client is pretty bad. It won't show me messages until it syncs everything (so I can't even see old messages while things sync), and, what's worse, it skips messages, and multi-device just doesn't work. My laptop just shows "Message could not be decrypted" until I delete everything and reset. I'm not sure why…
Have you checked if yours is up to date?