I have a Galaxy A40 and my charging speeds are fine. Does your phone get very hot? There could be some misbehaving apps on your phone, which could explain why Airplane Mode increases charging speeds. Check your battery usage on Device Care, if anything seems out of the ordinary, uninstall it and probably Factory Reset just in case. If your battery usage appears to be normal, you could have a defective power brick or cable. This is unlikely, since you have specified that a different cable yields the same results. This leaves us with a software issue, which seems strange because no other phone reviewers I have seen seem to have discovered this problem. I hope you find a solution to this problem...
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