mmmm, I know what you mean by one minute all working the next Frrrrttt.
Unfortunately thats the Miggy for you.
Regarding updating the Indivision, I agree with you in that only "major" updates will be flashed, felt uncomfortable enough flasing v1.1.
I think charlie is spot on regarding reflections, you will probably find another monitor OK, What to do about it If it's a captive cable I'm not sure but you could try making a custom shielded cable for the Indivision Output.
Regarding The shield... Ok this topic will probably cause a bone of contention among people but as an engineer, I must state that the A1200 was designed with it in place (mainly to meet higher german EMI standards / FCC). You may find without the shield your miggy can radiate more & interfere with other devices, random crashes may also occour due to pickup by the miggy from other devices, ex mobile phones, Wireless devices etc.
I did cut my shield & refitted it, I used a sharp heavy duty pair of scissors & used the punched holes as a means of creating the cut out. watch the sharp edges & ensure you blunt any points with pliers or suitable tools.
To see my shield cut out visit my profile photo album & look at the A1200 restoration project.
Now whether cutting & refitting the shield was pointless I don't know but I followed Jen's recomendation that it should be refitted. It also calmed my OCD