Hi Martin, I had some clear tonight so at 10 pm I set up M95 (east of meridian at that time) as a sequence in SGP.
On this occasion in Sitech I set the scope horizontal pointing Az 90 and parked it there. So my process was as follows:
unpark the mount (I used Sitech interface to do this)
In SGP, tick slave dome to scope, then in target settings click 'Centere now'
Scope moves quite quickly to target (as usual for me) - no pier flip.
Dome takes a while to catch up and before it does, SGP's centre now routine is taking an image of the inside of my dome.
I repeated this process three times with the same result each time.
So that wasn't particularly useful, it's similar to what you found, but I had no pier flip from Sitech up to that point of failure.
If it's clear again tomorrow night I'll park at Az 270 and centre on a target west of the meridian to see if the same happens on the west side.
I must admit I'll be surprised if it fails to wait on the west side as that's where I image mostly, and I'm sure I'd have spotted the problem before. I will check though.
Also tomorrow I'll post a pic of my mount parms dialog from Sitech.