Funny, (funny odd not funny Ha Ha) I had the exact same thing happen to me, same year RT too, It really did not take much and mine broke coming off. A few suggestions here but I don't see anyone who actually fixed it or did I mis read something. I like the magnet but I had not thought of reinforcing it with drywall tape or similar, good idea.
Mine is fixed.
Bent a small piece of plastic to use as a backer to the broken tab. I then used Plastaid to glue it all together.
I found it helpful to use the triangular battery cover to align the tabs while I glued them and the glue set up.
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