Kindle fire hd 7 inch 2nd gen charging issue topic

Hello all I am not a Kindle user but my mother wanted one for Christmas so I bought her one she cold only charge it to 74% so I did a factory restore on it, it worked fine a month later here we go again it only charges to 67% this time call amazon they blame it on a million other things nothing I can see and remind she only uses this for books no games or anything else anybody else have these issues.....seems to be a software glitch or something I know if I do a system restore it will probably fix the issue for awhile again any suggestions let me know thanks.
She has left it plugged in for 8 hours and it just stays at the same percent for anyone wondering if she left it plugged in lo general enough

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