Why do my system tray icons keep disappearing or turning blank?

Why do the icons in my Windows 10 system tray randomly vanish or turn into blank white squares? Sometimes they come back after a restart, sometimes they don't, and the hidden icon menu shows them as enabled but they never appear on the taskbar. I've already tried restarting Explorer, clearing the icon cache, and rebuilding the thumbnail database, but nothing has worked.

Could this be a shell extension conflict, a corrupted user profile, or something related to a recent Windows update? And is there a permanent fix that doesn't involve resetting the entire taskbar configuration?