If you’re using serial (or UART) communication between two devices and seeing data corruption, there could be a simple fix. For example you might be trying to communicate between two Arduino boards, using one Arduino Uno as a Serial-to-USB adapter for another board, or have an Arduino connected to a Raspberry PI.
If you’re getting corrupted transmissions that get worse at lower speeds, double-check you have common grounds between the boards. Inductive coupling is probably letting the communication work. Without the common ground though, your transmission is going to be susceptible to all kinds of noise.