Noter effect on strings?

Hello everyone, recently I was gently tuning my 3rd string from A back up to D, when it snapped. It’s a .012 steel string, which was what the original string was when I received the dulcimer. Dulcimer and string only about 6 months old. I’ve snapped strings before but that was before I had any understanding of what tension changes might be tolerable. I’ve tuned this string from DAD to DAA back to DAD several times without issue. This got me thinking:

I’d say I play 50% of time with a noter. Mostly using bamboo or the standard mcspadden or folkcraft noters. Is there any effect a noter can have on string integrity over time?

Ive replaced this string with another .012, and tuned it up to D over about 3 days (gun shy🙄). Any thoughts on what tuning “limits” would be with this string gauge? I think my VSL is 26 but I’ll have to check.

Thanks all!