Noise from behind drives when i turn on spindle (machine down)

Good day all,

I was wondering if anyone could help with this matter. I have a Giddings and Lewis Horizontal Mill that has been retrofitted with a Meldas 500 MItsubishi control. The issue that i am having is that every time i turn spindle on i am getting a loud high pitched screeching noise coming from the electrical box, behind the drives. I originally had an issue where i couldn't tap or orientate the spindle. SO i found the issue to be the spindle encoder. So i replaced that and everything ran fine for a few days. then i go to make a tool change and since then it has been making the noise. I am lost now. i have no idea on what it could be. Any suggestions? There is a rotary table on this machine that i am also trying to get up and running. Thank you and have a great day.