Dead zone: do you mean unresponsive or even black screen ?
You have probably read this on the web:
A dead zone on the left side of an iPhone SE screen is usually caused by a damaged digitizer, a faulty screen connector, or a minor software glitch. Quick fixes include removing screen protectors, performing a force restart, or getting a hardware repair.
Best would probably be to:
contact support, in it were a software glitch (but you changed OS, so unlikely)
or go to an Apple Store if there's one close to you.
It seems that's not an uncommon problem on iPhone SE3.
Topic:
Community
SubTopic:
Apple Developers
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