Cast on block Crash to Desktop

I have just tried swapping over to a Svalinn Crucible Tower Shield and anytime I try to add to the Cast on block skill sockets I Crash to Desktop.
Below are the Copy - Paste of the item in use.

Item Class: Shields
Rarity: Unique
Svalinn
Crucible Tower Shield
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Block chance: 26%
Armour: 265 (augmented)
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Requires: Level 78, 83 Str
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Sockets: S
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Item Level: 83
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Grants Skill: Raise Shield
Grants Skill: Cast on Block
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141% increased Armour
-13% to maximum Block chance
Block chance is Lucky
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The priests found the Great Shield the night it fell to Middengard,
but it was the smiths who delved into the secrets it held.