S7 shows charged percentage even with BATTERY REMOVED

Samsung Galaxy S7 owner here. At some point, the original battery got bloated, so I decided to replace it. After the replacement, with the new battery, the phone wouldn't charge and would turn off after as soon as I removed the charging cable. Charging percentage would show a random constant number (the favourite was between 57 and 60 but could vary).

So I took the new battery off and plugged the charger in without a battery attached. And guess what? The phone shows a random charged percentage (this time fav range is 35-40%).

Tried hard resetting, pressing the power button to drain the capacitors, clearing the cache, nothing helped so far. I am clueless where that number could come from and I am guessing that when the battery is hooked on, the phone doesn't even recognise it.

Any help appreciated!