Intermitent disconnection after battery replacement

Hi!

Last month I started having problems with my Switch Pro Controller. After a while without playing I couldn't get it to charge properly and at the end it stopped charging at all. I checked the battery and it was swollen so I order a replacement and change it as soon as possible.

However, after replacing the battery the controller has started to turn off intermittently. Sometimes just clicking any button turns it on but sometimes it takes it a while to work again.

Is the battery defective? Or it may be caused by an additional problem that needs a different fix?

Please let me know if you need aditional info about it adn thank you all in advance!