Random sims and cats/dogs from outside of my household keep coming into my house

I don't know if it's something to do with the "pet adoption drive" event which is happening currently in my game, or related to the "for rent" pack, but random stray cats and dogs keep entering my sims' house. I do not have any mods installed. I have tried adding the strays to my household temporarily so I can get my sims to stand outside of the house and call them over, and then tried locking the door to stop them being able to re-enter, and then removing the animals from my household again. But, this is ineffective. Other random NPCs also keep entering my house even though my sims have not invited them in, and there is no option to "send home" - the sims are usually neighbours, or the tenants of my sims' rental properties so I'm not sure if there is some sort of glitch allowing them to enter the house, even though I have not given them permission to enter/giving them keys to my residence. Any ideas?? 

For additional context, I am playing on PC and I do not have any mods etc installed, just official sims 4 expansions etc.