m16 R1, charging then not charging, repeating rapidly

Hi, my Alienware m16 R1 had this problem last year, long enough for me to forget the exact date. When I was playing Helldivers2 or some other games, it suddenly got laggy for a sec, and recovered for a sec, then got laggy again. I found it was because the laptop suddenly stopped charging at the moment: it just stoped, then resumed, and then stopped again, repeating. It didn't last for long at first, but happened everyday, and everyday it lasted longer. I called Dell Support for help, he told me maybe updating bios can fix this problem, and it turned out to be true, until recently this happened again.

Last month when I was playing as always, this happened again. For several days it grew worse. July 24th, it lasted for almost half an hour, and the power button was blinking in a sequence that shows reds 1 time and blue 4 times repeatedly. I was quite confused when I found this showing something wrong with my screen, and my screen had no problem at that time. I called Dell Support again, and he told me to check my bios to see the battery's information, which seems all good. He can't tell why this is happening, so he can only suggest to update bios one more time. I did it, and this bad situation stopped for several days.

Recently, should be one day last week, this happened again. Battery charges and stops charging repeatedly. I can hardly enjoy my games in such case, so I called Dell Support again. He told me it might be something wrong with my battery. I don't know if I can trust him, because in those two times I called before, neither told me it's a battery situation, and this time I didn't say anything more than last time. If it is because of my battery, then why updating bios can help fix this? These days when it happens, I reboot to check the bios, and find nothing wrong. I've heard that 4 reds and 1 blue means something wrong with battery, but in my case, it is 1 red and 4 blues. Also, this happens in a sudden, and ends in a sudden, so everytime I reboot my computer, it's already stopped.

I just want to know if it's really because of the battery or not, in case I spend money replacing my battery, only to find this happen again. Dell Support suggest me to take a test at service center, and I will go there this Saturday. If someone has met a similiar case, please let me know how you solve it. It's really bothering me for a long time, destorying my game experience.