If android stops booting unless the bootloader is unlocked then something you guys have done has modified the boot partition in some way. My guess is that ext2fsd mounts the boot partition and updates the mount time fields and stuff in its super block, causing the secure boot to fail.
Yepp. Thats why I asked him about if he rooted. Then I was like, did the stupid Ext2fsd he installed under Windows change something on those partitions? Seriously? I guess mounting them on Windows means Ext2fsd does at least one write task to them, or he wrote something to them. Meaning the bootloader detected a change to the partition and didn’t boot Android because of security reasons.