Yalu102 jailbreak for iOS 10 â 10.2 brings its own share of bugs and compatibility issues with certain jailbreak tweaks and packages that have not been updated to support the latest jailbroken firmware. As a result, it is imperative to boot into Substrate Safe Mode in order to break away from nagging issues such as boot loops and system freezes after jailbreaking your iPhone, iPad or iPod Touch using yalu102.
As a prerequisite, all affected users are advised to update their iOS 10.2 Substrate Safe Mode to the latest version (0.9.6000), which introduces support for yalu102 jailbreak.
Here are the steps to use latest version of Substrate Safe Mode on iOS 10.2 jailbroken device:
Step 1: If you have already rebooted the device after facing issues with your jailbroken device, then it will be in a non-jailbroken state owing to the semi-tethered functionality of yalu102. On the contrary, you need to reboot your iPhone or iPad to enter non-jailbreak mode if you have not done it already.
Step 2: Once you have rebooted into the non-jailbroken state, just launch the yalu102 jailbreak app from the Home screen.
Step 3: After launching the yalu102 app, just tap the go button and then instantly press and hold the Volume Up and Power buttons together in order to boot your iOS device into Substrate Safe Mode.
Step 4: Continue to press and hold the two buttons until the Apple boot logo screen appears on the device, followed by the Lock screen.
That's it. Your iOS device is now successfully booted into Substrate Safe Mode and you can easily isolate or fix the issue you are facing on your jailbroken device by uninstalling or removing incompatible jailbreak tweaks or apps installed on the device.
[Source: Redmond Pie]