Understanding NetworkReader:ReadByte out of range errors

I regularly have errors like this:

It happens when changing any line of code in a script, even though it's not changing anything about the networking functionality. Creating a new build normally solves the problem.

For example I added some debug logging to debug my client interpolation, but adding a simple print() command already breaks compatibility with the build, where the server is...

Understanding NetworkReader:ReadByte out of range errors