Why is the paste not working in google sheets?

I was pasting in data from the internet into my spreadsheet and google sheets (or Firefox) is pasting in said data ''three times'' and it is driving me insane. I paste the raw values in a formatted cell, and rapidly it pastes correctly, but then pastes the original data/cell at least once if not twice. Like, say there's a green cell and I paste the values in it, and it works, but it then pastes the data OVER the cell removing the formatting. The worst part? It works correctly on chrome!