A number of people have reported on GitHub that their 9250-fitted devices show magnetometer issues on start-up, and sit frozen in the "auto bias" phase indefinitely. It seems to be a marginal issue that doesn't affect all MPU-9250 devices and we suspect it related to the physical hardware ICs and production tolerances. Thanks to a community member (sir-maniac, thank you!) it appears that by merging in some changes as part of the Invensense 6.1.2 motion drivers improves/fixes the issue.
To that end, we have put up in place a development firmware for all devices. This can be access via the GUI by putting it into DEV mode (under the about menu), which will reveal the additional firmwares in the flash drop-down. If you feel you are having issues, give them a try. We'd be interested to hear feedback on whether it addresses your problem. You can always revert back to the current production firmware (v4.0.5 for 9x50 users, 2.20.9 for 6050 users) if you have a problem.
As a side-note, please be advised that we will be deprecating the 6050 and 9150 instructions and firmwares this year. The source code will remain available, but we will reduce down the website and instructions to simplify things - the reality is, very few people are building 6050 and 9150 devices any more. The MPU-9150 chip has been retired from production, and the results from the mPU-6050 (without a magnetometer) are not great when compared to the 9250.