I'm a new developer at an agency and have been having this issue with the Shopify CLI since I begun in January. I'm running WSL2 on Windows 10, making sure I followed this guide to install my Shopify CLI.
Basically when running 'shopify theme serve' after the initial files are synced, nothing gets synced from that point onwards. To get around this I have to ctrl + c out of the serve and then 'shopify theme serve' again. This drastically slows me down when developing.
Something I've noticed with it is that I don't think I've ever seen a .liquid file sync when serving the theme (I see .js and .css files sync only after shutting a serve down and running it again, never once seen a .liquid file among them).
I had to sanity check that it wasn't the laptop, I did a fresh install on my personal PC, and ran into the exact same problem, which makes me think something is wrong with my install process. If anyone else is running on WSL, is there something I'm missing when it comes to this install process?