I tried an experiment
I took a Recompiled.SHP generated by v.83 and loaded it into SHPedit with the NO flash box checked
I added a new Icon hull and turret into the shp and saved
I then ran it through MOBHack then the game with a special unit made for the hybrid Icon I added as a test
All the icons that were in the Recompiled.SHP that I had added an icon with SHPEdit were normal in MOBHack
The images that were already in the Recompiled.SHP still exhibited the kruf as before when viewed in the game
I changed the grey to fushia to make the areas it is in show more clearly.... it is not just the turret that has the problem.
it is every pixel within the boundary of the X and Y of the image that does not have part of the icon in it that shows fushia same as if you drew a box with the max X and Y of the image then dropped the image on top of that..... any area of the background that was left unused by the image shows the grey flashing colour
The hybrid I added with SHPedit with the NO flash box checked was OK in MOBHack and the game
I think you are close to getting this solved and if it helps, Fred had some problems I help him sort out with his first version of SHPedit as well....... not quite as odd as this but there were issues that needed resolving and they were and you will too
The issue is that area within the max X and Y of the image that does not have Icon detail. Get that sorted and you are nearly there
FURTHER
I built this test to show it's the X-Y
That is just four 4 pixel squares at the outer boundary with XXX in between for the hull and the same for the turret except that uses 2 XX
Don