Why is my iPhone SE reboots itself / won't charge?

Hi everyone,

After replacing my Iphone SE IOS 12.1.2 battery, I have the following issue :

• The phone reboots itself every 5 minutes approx., while using it or not, plugged in or not.
• The battery is stuck around 13% and won’t load

I’ve tried to :

• Change the cable and charger, wall charger or USB plugged in my Mac -> same
• Plug back the old stock battery -> same issue (what?!)
• Softly brush the charging port to clean it-> same
• Installed a new battery (so the 3rd one) -> same
• Hard Reset -> same
• DFU Restore -> same

Other :

• The battery state is “Service” in IOS parameters (for the 3 batteries…)
• Doesn’t seem to have this issue when plugged in my Mac, while in Itunes restore mode (the one with the Itunes logo on the phone screen). NOT 100% SURE.

Do you know what may be the cause(s) of this issue and what may be the solutions ? Maybe we can discard a battery issue as it appears on 3 different batteries.