react native project doesn't sync on emulating platform after saving files

I have joined a React Native project recently, and have just installed everything to make compiling and testing possible. But I have one problem that my colleague‏‏‏‏s don't have - when I try to save my code changes, what I worked on doesn't appear to have changed on the emulated platform (Genymotion), and only after I re-run

yarn android

the code syncs on the platform.

Any reason as to why that happens and how that can be fixed?