spirit shield bug

i have been trying to get the 35 fcr spirit on a monarch shield and since i didn't get it i was removing the runes with hel rune and after i got back the base, the defense of the shield decreases with every removement of the runes and i ended up having a monarch shield with just 19 defense instead of 211
how can i maintain the original defense of the shield without dropping it by removing the runes ?

 

That only happens to ethereal items, without the 'enhanced defense' mod among runeword mods.
Find a non-ethereal (normal or superior) one and you won't face this issue. Anyway, a common practice is to use eth monarch spirit on switch, with CtA, in which case the fact that it has 19 defense does not matter.

 

i am using eth cuz it requires less str than a normal one (146 str req compared to the non eth 156) and after it s broken just find another one is easy to find.
ok so only to eth items is the bug.
thanks for the answer