Almost sounds like a wiring issue.
Have you got a chance to make sure the main charging wire from the alternator to the battery is in good condition and attached securely? If not take a look at that wire as well as the battery terminals.
I have attached the charging system wiring diagram for your reference. Also included diagnostics steps.
Please let me know if you are able to get this resolved.
Images (Click to enlarge)
Wednesday, July 21st, 2021 AT 5:28 PM