DSi with R4i won't stay on sleep mode

back in 2014 I bought a DSi and I knew nothing about flashcarts except for "R4 plays DS ROMS" so ofc I bought the cheapest one and I got this one:

Image may be NSFW.
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(Website on the R4 is www.r4isdhc.com.cn )

And it had been working just fine as far as I remember. Last time I played with the thing was like early last year. I've been keeping the battery charged, though.

Anyway, now everytime I'm playing and close the lid on my...

DSi with R4i won't stay on sleep mode