Nope, no fix as of now...unfortunately

The keys charge inductively through the ignition, so you guys may just need to replace the rechargeable battery. The older style keys like on my E34 have an actual red LED, so when the range decreases or the light gets dim, I know its time to replace it. Unfortunately the batteries in the newer style keys aren't a simple watch battery, so you'll have to disassemble it and take a look. I'm replying via my phone, but I'm guessing there might be a writeup to fix the key on www.e38.org...might be worth trying, otherwise good ol' Google using different keywords.