Safety cutoff started to burn

Hi everyone,

I have a makerbot 3D printer and yesterday when I printed PLA my safety cutoff started to burn. Does someone have already had that ? Do you know why this happened ?
I join a picture of my safety cutoff.(sorry for the quality of the pix)

It is the first time that it's happened whereas I have already printed a lot of parts in ABS and PLA.

Thanks in advance,

Anais

... most common exceeded current limitation of traces, wires or terminals ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

So, wait... The safety cutoff, meant to prevent the hot-end from burning up, burnt up?

Did no one think it wise to add a fuse to limit the current?
(pardon my ignorance, not versed in Makerbot electronics)