My Land Cruiser's electrical system is acting up – need expert advice

I've got a 2015 Land Cruiser that's been absolutely bulletproof for the past 200,000 kms, but over the last couple of months it's started developing some really strange electrical behavior that's got me worried. The battery light flickers on and off randomly, sometimes the power windows won't respond to the switches, and on two occasions the car just refused to start even though the battery was showing full voltage on my multimeter. I've checked the alternator and it seems to be charging properly, so I'm thinking there might be a deeper issue with the wiring harness or maybe a faulty BCM that's causing all these intermittent problems. I'm not an electrical expert by any means, but I've done some basic troubleshooting and I'm starting to think this is beyond my DIY skills. I was planning to take it to a specialist who deals with these complex electrical issues, and I came across a workshop that seems to have a good reputation for handling modern vehicle electronics. I wanted to learn more about their diagnostic process before booking it in, because I've been burned before by places that just start replacing parts without actually finding the root cause. Has anyone else experienced similar electrical gremlins on their Land Cruiser, and if so, what ended up being the issue? I'm hoping it's something straightforward rather than a complete wiring overhaul.