UNO R3 TX light stays on after uploading

Hello. I'm using FLIP to upload a piece of code on my UNO R3. I have been working with some code for a while and it used to work fine, but recently after I made some modifications to it and tried to upload it, it stopped working. I have noticed that as soon as I select communication medium (USB) and click on "Open", the RX, and TX lights turn on. Afterwards when I "Run" the Operations Flow, the RX light turns off and TX light stays on. Both lights used to turn off before. I thought I messed up my board somehow, so I bought a new one today, and after the first upload, it started happening to it as well. Even when I try to use the old code that was working before, the same thing happens with it as well.

I am very new to microcontrollers and I would really appreciate some help regarding this situation. What could I do to fix this?

I can more than likely not help you but for me to understand.

You're reprogramming the 16U2 with your own code?

Hello. Thank you for your reply. I have been using this library and following the instructions from

Basically what it does is that it acts as a controller for Nintendo Switch to do some tasks in game. It turns arduino into an actual controller connected to the console.