DQ VI problem recruiting monsters

I’ve read a couple of FAQs on recruting monsters in DQ VI. T

Stahlbaum’s FAQ says:

"You must have mastered the Beastmaster class and
have an available slot open in the wagon in order to capture a monster. "

the DQ VI shrine says
“To recruit monsters, you must have a Beastmaster and the wagon must be available. You must have at least one empty slot to recruit the monster.”

Does this mean that I have to have space in the wagon or at maximum 3 characters in the field?

Right now, I’ve got a mastered Beastmaster. Party contains Hero, Hassan, Muriel, Chamoro and Amos. I’m trying to recruit Homini slimes outside of Monstoru with no luck. Any help would be appreciated!