Answer to "Why does my G400s connect and disconnect randomly?"There may be an issue with the mouse cable. Try replacing it according to this guide.
Answer to "Why does my mouse not move smoothly?"There may be an issue with the mouse feet. Try replacing them according to this guide.
Answer to "The buttons on my G400s do not feel crisp when pressed?"Grime is most likely preventing the button from functioning correctly. Try disassembling the mouse according to this guide and then clean the problematic buttons with rubbing alcohol.