Ok, here is my little trick. I don't know if it could help. If you have a cwm backup, just restore boot.img partition Or you could flash a custom kernel. your wifi key will be reseted. Because I did it a few times.
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Device: Galaxy S5 G900I
ROM: XtreStoLite ROM by @edgarf28
Kernel: KT Kernel by @ktoonsez with modified ktoonsifized v2 profile