Why did it arched? How did you notice that, SWr flictuating? Mine has the insulation backwards from factory.. Even upside down it, it works fine.
It arched thru (burned a hole thru) the upper insulator ...
Running too much high power too many times.
I saw it instantly when the VSWR reading shot up to over 30:1 when I was transmitting.
I immediately unkeyed and shut down for an inspection.
With my binoculars from the ground, I could see the dark carboned area around the vertical radial just above the ground radial plate where it had arched severely.
Upside down insulator will let the antenna perform just fine,
UNTIL, it gets wet or during an active rain the VSWR WILL climb to higher readings.
You might claim it doesn't, but it is virtually impossible for it not to.
The water on top of the horizontal radial plate will be a direct connection between the radiating element and the ground elements. Water conducts, electricity and RF .......