BOOTLOOP. Not sure if soft or hard issue

LG F400L (Korean Variant)

I've had random reboot issues before but very rarely. It only occured during turning on the wi-fi and making a call at the same time.

2 days ago I went from Cloudy 2.5 (L) to Fulmics 5.0 (M), restored all my apps and my settings, then after a day, the bootloop issues started to occur. Sometimes it works and I'm able to use the phone for 1-2 minutes but then it would start bootlooping again (NONSTOP). So i thought the problem had something to do with the ROM so I restored my backup, went back to the Cloudy 2.5 ROM, same settings but SAME ISSUE. :mad:

But I found out that, it works when it is plugged in (charging). Even I load it with a lot of apps, no problem, but as soon as I remove it from being charged, it would start bootlooping.

I just need to know what could possibly be the issue?

BATTERY? (Replace the battery)
ROM? (Flash the original Kitkat via download mode)
or somethings else..

and would it help if I post a log?

Thanks. I am in desperate need of an answer :(:(:(

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