Yeah it definitely sounds like a corrupt card reader, or micro sd card
Have used to have 2 R4's with bundled Kingston 1gb cards ( sure now that they are fakes anyways as they were shipped from HK ) and both the micro sd readers and full size SD adapters were giving me errors and the R4 couldn't...
I am trying to hack Fire Emblem Warriors on my 2DS XL, I have been trying to get it to work, but I need some extra help figuring it out. I have HEX codes, and a possibly outdated plugin, but I dont know how to implement them