Fix boot loop of macOS updater The latest macOS 10.13.2 update apparently didn't install well on my MacBook Pro 13" with Touchbar. 

On every boot the system loads the update installer but gives then an error message that the install file was not found. Since the update installer would load automatically on every boot this results in a boot loop. However I figured out that I can force to boot into macOS with ALT+R which has been a temporary fix for me since then.

How can I fix this? Is there a way to delete downloaded update files?
Try starting your Mac in Safe Mode, and see if that fixes your issue. To start in Safe Mode, hold the Shift during startup.

If that doesn't work, start the Mac in single-user mode by holding Command + s keys, and see if you can have the updates installed there.

Apple Support Document, Mac startup key combinations lists various startup modes and required key combinations.