Merms in caves wont come out there houses at all

I put them under a cave enterance light and that wont work either, although they are ment to be able to spawn without the ligh,and no it isnt winter and no its not guard merms, there regualar merm houses made by wurt,they come out when you hammer them though, this is really annoying for when you want to make a merm base in the caves as wurt,thank you!