Pablo,

Good new, Bad news.

I finally found my 12F683 and gave it a go.
I've completely duplicated your problem. Blinking and all.

For some reason it only does it on the 683.
Every other chip I tried seems to work fine.

And the bad news is, I haven't found out why yet. (Operative word, Yet)
It appears to be with the A/D, the readings are all over the place at low voltage input.

I still have many things to try, but just wanted you to know you're not crazy.
And, I WILL find it. (unless somebody beats me to it)
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