Thanks for the chapter!
If they were afraid of it flying away after turning back into a monster, why didn't they just find a secure room with a strong ceiling to have it change in? In LN, Olga was a young man running the counter at a used cart shop who was somewhat worried about his father due to his father spending several hours in a dungeon but having been gone for days. Helping him get both kind of rocks was still the same.
Granted having a magic cart that can hold more than the space it takes is great, but he really should invest in a cart that shares his drop rate with his party members in a large area. Just think how happy Eve would be from all the S class carrots she and the others could collect! XD Seriously though, when fighting boss class monsters it would help increase the drop chances and quality without having MC take it out. Primarily this would allow the others to get their own seed drops and increase their statuses.