the same happened to me. Swollen battery and support advised to replace the whole thing.
Bob2022 provided really good photos of the teardown in this thread:
The battery has 2 strips of double side tape Attached to the visible tabs, but the tabs are not helpful to remove the pack.
DIY removal at your own risk. Things get risky from here.
i pried up the battery with a lot of force without damage. If i were to try it again, i would try a solvent or some piano wire to use less force. There is no electronics under the battery.
The pack is is 2 8.3mm * 49mm *64mm lithium packs (3500mah * 3.7v) with tabs welded to a custom pcb. The pcb routes each battery to a single black/red pair on the 5pin connector. The yellow pin is ties to a sensor thar was kapton taped between the 2 backs. The board has pos/neg clearly labbeled.
Carefully snipping and lifting away the blue shrinkwrap and kapton tape, you'll find the 2 battery packs are also double side taped to each other. Leave them. Instead, snip the tabs off the PCB (space as needed, i snipped closer to the battery to give me more working space.
In theory, you can rebuild the pack with 2 new 834964 batteries. I haven't found those yet, but have gotten it to temporarily work with a pair of smaller battery packs i bought for another project.
Currently i am looking for more exact replacement packs or info on how the charging circuit works to make sure i find something safely compatible. I've sent out a few inquiries, but the only source i have found wants orders of 1000pcs.