Hi @scumbag1,
It may be that the battery is failing and needs to be replaced.
How old is the speaker? Even rechargeable batteries have a lifespan.
Here’s the Ifixit [guide|119228] guide, if you decide to try replacing the battery.
Replacement batteries are available online (also from Ifixit - see the guide above). Just search for ''JBL Charge 4 Battery part'' to get results for suppliers that suit you best