It appears this has been reintroduced in 18.6.2 https://developer.apple.com/forums/thread/756309?answerId=856198022#856198022

As of 18.6.2 it seems that the issue is back unfortunately.

This is still not fixed as of 18.6.2. At this point, I have no idea how anyone is building Safari Web Extensions for iOS. I can't reliably call my APIs after 30 seconds.

I'm still seeing the issue in 17.6.1 18.0 Seems to be working better.

Same. Background script still becomes unresponsive.

Sorry for the formatting... This forums app is interesting.

@radiolondra your post and work in this space is well known on my team! Thanks for this. Your language towards a "well structured MV3 Service Worker" is that the heart of my post here. Looking through my minimal-reproducible example you'll see I'm able to reproduce this issue with 10-20 lines of total code. Do you see anything in there that would cause this? In the meanwhile I'll explore your work arounds. Thanks!

Same exact problem here. For some reason the background script simply stops responding to sendMessage randomly. Can't figure out why.