What ABI are you using for your userland/kernel?earm allows unaligned access whereas the old ABI didn't - looking back at an old dmesg it looks like you're using OABI. As it won't be (isn't?) supported for much longer you should switch.
To my understanding I use the current ABI. The init is:/sbin/init: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /libexec/ld.elf_so, for NetBSD 7.99.53, compiled for: earm, not stripped
The kernel is:netbsd: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, for NetBSD 7.99.59, not stripped
I can't boot NetBSD 6 kernel with the userland of my SD card. Afaik NetBSD 6 still uses the older ABI.
Best Regards Stephan