Two totally seperate and independent issues covered in this topic, one of which was solved.
When you repair an item, it resets its stats and all its characteristics back to the default template stats. This includes the "Switch group" and the owner if it is soulbound.
The fix was to stop the loss of thos attributes.
The second issue was as to why the items was destroyed while being repaired. Without being able to observe or repeat the activity I am not able to say whether it is an operator or system problem. Hence I ignored it and hoped it went away. This worked - until now