Cathy2K errors

I have installed Arduboy homemade package 1.2.8 to use Cathy2K bootloader. It works fine on emulator and shows 30720 bytes of overall space. But when i uploaded sketch on real Arduboy i have an errors after i exceed 28934 bytes:

avrdude: verification error, first mismatch at byte 0x7000
         0x55 != 0x10
avrdude: verification error; content mismatch
avrdude: verification error; content mismatch

Can anyone help me to find tiny bootloader or to fix this errors?

Is your Arduboy an Arduboy FX or a ‘classic’ Arduboy?

Either way, odds are your Arduboy itself doesn’t have the Cathy2K bootloader installed, and the bootloader it does have installed occupies more memory. The default bootloader for a ‘classic’ Arduboy uses a 4KB bootloader (leaving 28KB of user space) and the default bootloader for an Arduboy FX uses a 3KB bootloader (leaving 29KB of user space).

A bootloader can’t be installed on an Arduboy like an ordinary program, it needs a special installation process using a second device (e.g. another Arduino board) that acts as an ISP/ICSP (in-system programming/in-circuit serial programming) programmer.