process stuck after copying large text

If you open a file .txt larger than 300 kilobytes, press ctrl+a then press ctrl+c and close the window (click on the cross at the top of the window) the window closes, but the process itself continues to hang in the task manager and it is impossible to open the program again until you kill the process. This happens regardless of whether you paste the copied text somewhere or not. If you select from the context menu select all and copy, the behavior is similar. Frozen process is consuming processor resources. If you copy a small piece of text, this does not happen. mousepad 0.5.8 encoding UTF-8