Screen working inconsistently after battery replacement

I replaced the battery in my Samsung Galaxy S21 Ultra after powering it on I saw no issues I used it for around 20 minutes before the screen displayed black, the phone was still on and the haptic feedback was still working when I unlocked it with the fingerprint sensor. I opened the back of the phone again and reseeded all the ribbon connectors and put the old battery back with no improvement. I left the phone sitting for around a month before changing it again this time it power down with no obvious issues but once again after 20 minutes the screen went black.