The Bolt batteries were randomly catching fire. Random news article about it [0].

[0] https://www.cnbc.com/2021/09/15/gm-advising-some-bolt-ev-own...

Sodium ion is much safer. Electrolytes in it may still be flammable, but CATL says there should be no thermal runaway or spontaneous combustion like Lithium-Ion. They’re also safer to ship without the hazmat warnings in the packaging.