Hey! I've been making games as a hobby for many years - mainly for game jams, however, this is my first BIG project.
(Won't be sharing what those games were; let's say it's like the vtuber rule of not mentioning past lives)
Missing sprites are generally because your device isn't able to handle all the textures, so the VRAM fails to render them.
In the main menu, go to settings and try to change the Quality to Half and check if the issue persists!!