How to best fix iPhone 8 vibration failure?

Last week, we received an iPhone 8, which with vibration failure. The fault detail is that the iPhone 8 has no vibration, we need to fix it.

Try changing a vibrator first, we found there really exist a problem with the motherboard. We only replace with the iPhone vibrator IC first.

Take a junk iPhone motherboard, so we can remove some useful component from it, and then we can use it.

Remove the iPhone vibrator IC from the iPhone 8 motherboard, and then install the new iPhone vibrator IC. Install the iPhone 8, turn it on, and test it, seems it works.

Go to Settings, test vibration for some Apps, some of them are working, but some not. What's trouble? Is the problem of the iPhone vibrator IC?

Disassemble the iPhone 8, and then use digital multimeter to measure the resistance value, the resistance value tested is normal.

Install the new iPhone vibrator IC, and then test the iPhone 8, the iPhone vibration function is still not working.

Try to fix it by replacing the new vibrator, after replacement, install the iPhone 8 and test it, now the iPhone vibration function works good.

Continue to test other functions on iPhone 8, all works perfectly, the problem has been fixed!