iPhone 7 audio IC repair

I have an iPhone 7 with classic audio ic problem. Speaker greyed out, took ages to start. As usual I removed the big audio ic, did 4 jumpers, reballed the ic and put it back. The speaker worked fine after audio ic repair. But it only worked fine for about an hour, then suddenly the phone automatically restarted, after restart the speaker greyed out again!

I thought I probably didn’t soldered it properly, so did the whole process one more time, again the speaker works fine for about half an hour to one hour, then the phone restarted by itself, and speaker problem came back again!! I did the job 3 times, each time with the same result, speaker only worked for a little while then stopped. I checked the audio ic pads on motherboard, no pad missing, all 4 jumpers were very well soldered, no loose jumpers. I also checked the resistance value of the 4 jumpers, all seem correct. The thing is, I already repaired lots of iPhone 7 audio ic before (probably hundred of them), all successful, no returns. This one is very strange, I don’t understand why it failed within just an hour.

I want to ask, apart from audio ic, is it possible that somewhere else on motherboard is not right?