My hunch is that your problem was caused by Boot Repair. Under some circumstances, Boot Repair will back up the Windows boot loader to a non-standard name and put a copy of GRUB in the Windows boot loader's place. Boot Repair does this to overcome bugs in some EFIs. It's an ugly workaround to, but not really a fix for, those bugs.
What I think may have happened is that you applied that fix in the past, but when the regular Ubuntu update came around, it replaced the changes made by Boot Repair with a more standard configuration. The regular Ubuntu update didn't recognize the Boot Repair changes and so created an entry for "Windows" that pointed to the regular Windows filename -- which was really just the old copy of GRUB installed by Boot Repair. This would result in exactly the symptoms you describe. Re-running Boot Repair reset things to the way Boot Repair liked.
If I'm right about this, then you're likely to run into this problem repeatedly in the future. You may want to check your boot loader files. From Ubuntu, the Windows boot loader is /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi. If there's another file in the same location with a similar name (I believe Boot Repair uses bkpbootmgfw.efi), then that's evidence that my hypothesis is correct. If so, you might try undoing Boot Repair's workaround. There's an option for this on the Advanced menu of Boot Repair. It's called something like "restore backed-up boot loader files" (I don't recall the exact term). OTOH, if you do this and your firmware is defective, then you'll end up with a system that won't boot Ubuntu. If so, your best solution is to return the computer to the store for a refund, since the machine is defective. If you're outside of the return period, write to the manufacturer and demand a repaired firmware. You won't get it, but there's a slim chance that the complaint will help set some wheels into motion that will result in fixes at some point in the future.
