Servo Variable Frequency Drive Plus retrofit kit for Bridgeport type milling machine

I have had the Servo VFD+ retrofit on my Bridgeport type mill since August 2023. The retrofit is a good complement to the Centroid 3 axis retrofit that is on the machine. I bought the kit including the 3hp 230v, 1ph, inverter rated motor. Five different speeds can be programmed at the included manual control. That ability has greatly reduced cycle times. Spindle speeds can be set far more accurately than the original Vari-speed pulley system. I can get speeds up to 5000 rpm. I have cut mold cavities with spindle speed of 4500 rpm. Run time over 2 hours, without overheating the spindle. The original variable speed pulley system could only reach 4200 rpm, but for only about 5 minutes before the spindle overheats. The VFD system also runs a lot quieter than the original variable speed pulley system. The variable speed pulley system makes a lot of heat and noise. I am having one difficulty with the control. When one of the selections, PS1 - PS4, are being used, the control will unexpectedly switch to the main control setting, while the spindle is turning. When this happens, the spindle will slow way down to almost stop, before the spindle speed set at the main control begins. It is a problem because if it isn't caught soon enough, there will be a broken cutter, or damaged part. Then, if the main control is set at a high speed, the cutter will take off at that speed to potentially get burned up (if slowing down didn't break it). When I ordered the kit, my ultimate goal was to connect the VFD to the Centroid control so that the spindle can be controlled by the CNC program, rather than controlling the spindle manually. My Centroid dealer was very helpful in getting me the proper diagrams and documentation for the connections. I was not able to complete the connections because I could not get the original wires disconnected from the inverter. The connection block on the inverter is very small and delicate. I was afraid of breaking it, so I stopped. I am still running programs by manually operating the spindle.