bashrc not loaded in /bin/bash shell

the ~/.bashrc file is loaded for interactive non-login shells, that's why running /bin/bash from ssh works as you expect.

For login shells (amongst others) ~/.bash_profile is read. Typically your ~/.bash_profile contains something like

if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

Which ensures that ~/.bashrc is loaded if your shell is a login shell.

If your ~/.bash_profile contains the above and ~/.bashrc is not being loaded you can debug the scripts by using set -x as usual.