The enabled auto center on the meridian flip options requires platesolving - hence your earlier error message. If you uncheck that, the mount just simply slews round to its flip position. The actions of the mount also require the flipping points to be set up on the mount for safe operation:
On my MX, I have the meridian flip points set to about 45 minutes (in time) past the meridian on each side. In SGP, I have the meridian flip point set to about 10 minutes. Since none of my exposures last longer than 30 minutes, it is always safe to flip (safety on flips has to be considered before and after the flip.) Your time of 5000 seconds is 83 minutes and probably is causing issues - as it could potentially try to slew 83/4 degrees past the meridian.
Try disabling the auto center and reduce the exposure time to 300 seconds and try again.