/gamerule mobGrief true wont update

i recently got a realm to play with my friends. Me and 2 others spent the first fortnight building an adventure dungeon for everyone else. when it was finally done i set /gamerule mobGrief to false because we had a wither boss for them to fight and didnt want it blowing up everything we had made. that was 2 weeks ago, i have tried everything i could think of and delved all through the internet but when i type /gamerule mobGrief true i get a message saying my gamerule has been updated but still nothing can gried. i didnt mind not having the creepers blow things up but according to the wiki it prevents my villagers from breeding so i really need to fix this. please help as i really dont want to reset to an earlier version before i did the rule, like i said, its been nearly two weeks since i changed it and people have built alot