Brush Tool Lags after a while using the program

Picked up Aseprite again after a long time not using it cause I wanted to work on my pixel art skills. Everything was going fine until the brush tool started to lag, it wasn’t noticeable at first but soon after it basically became unusable. It never did this when I used this program before by the way. It was only the brush tool as all the other brushes worked fine without lag, also I tried my other art programs just in case it wasn’t my computer being bad and they were all fine.