2400MP Keystone Issues

When I use any keystone setting I get the ghost of a blue & clear pattern, possibly with small writing on it, overlaying my display. It's present with or without a signal. I thought it went away when I did a factory reset in the past, but now it's there whenever I keystone. It doesn't seem to be present for the first second or two of auto-keystone though.

Could it be a residual image stuck in a buffer or am I missing something simple to clear it?

Thanks for your help.