Mini Roadster starting issues Terminal 30

Terminal 30 issues on these can be tricky. I had something similar happen with my Mini Roadster. Have you checked for any significant voltage drop across the circuit breaker when the starter motor is engaged?

Voltage drop, how would I check that exactly?

You'd need a multimeter to measure it. However, considering the symptoms, it's probably best to get the charging system properly diagnosed at a workshop. Could save you time and potential misdiagnosis.

Thanks for the advice. Turns out the power supply was faulty and causing the issue. Got it sorted at the workshop for 290€, all in. Starts perfectly now.