NEED HELP- S-Spindle error

Hey everyone, I have a Fadal 4020 and I keep getting and S-Spindle error quite often. I keep having to do an M84 to solve the problem but it only works temperately. It seems every so often when it does a tool change it cant find home for the spindle, and then errors out. This has become quite the problem and it would be great if someone might be able to explain why this happens.

-Thanks

I have had the same thing with my Fadal 4020. It may be a faulty hall effect switch on the spindle orientation. check it, it may need replacing. You can get one for $35 from FadalCNC.