There is not a BSOD or reboot loop related known issue on Microsoft KB5004945 document, only input, Edge and printer related known issue.
https://support.microsoft.com/en-us/topic/july-6-2021-kb5004945-os-builds-19041-1083-19042-1083-and-19043-1083-out-of-band-44b34928-0a71-4473-aa22-ecf3b83eed0e
So the reboot loop issue on a few users is just an individual phenomenon, don’t need to worry about.
Maybe there is a third-party software conflict or driver compatibility issue on those users’ devices, you could compare their devices with other normal devices. Or just enter WinRE to uninstall KB5004945 or restore system to a healthy timepoint, once boot normally, pause update for 7 days, wait for another new update from Microsoft.
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