Hi Rilwis, thank you very much for your reply.
For some uknown reason I had defined like this:
define( 'RWMB_DIR', trailingslashit( get_template_directory() ) . 'inc/plugins/meta-box/' );
define( 'RWMB_URL', trailingslashit( get_template_directory() ) . 'inc/plugins/meta-box/' );
Which trailingslashit function made all those wrong url's, have no clue why I did this, probably in a hurry and did not double checked, now is all good, thanks for the heads up. Thanks!