Laptop turns off suddenly when there's plenty of battery life left

So i've been searching article after article for an solution to this but still a no go. My Toshiba Portege R930 turns off suddenly when it's anywhere around 60-70% charged when operating on just the battery and the mains is disconnected. All the posts i've read suggest faulty batteries, to which the OP's mostly reply that they've change the battery and still have the same problem, like myself. I bought a brand new battery and when the laptop is unplugged from the mains and left to battery usage alone, it still turns off at 3 quarters full. The battery also looks like it drains a lot faster than it used to. I noticed these changes, the sudden power off included, after the windows update 1909 a few months ago... it could have possibly happened before that, but to the best of my memory it was after the update. When I turn the laptop back on after it has shut down automatically, it'll last a few seconds before turning off again, however, if the mains is plugged in, it will stay on. Once charged again at 100%, on battery alone the laptop will operate until it goes to half-3 quarters full again. I'm wondering if anyone has had this problem, or at least found a solution for it? It was too late to roll back to a previous version of windows, so instead I "reset this pc". Unfortunately, as soon as it booted back up after the reset, it was right back at 1909 as it decided to update windows before I could even use it So that was a waste of time. Does anyone have any knowledge of what specific files in the latest windows update that could be causing this?