Had not exactly the same issue. It may depend the kind of animals. I use often foxes inside my base and around for hauling, these are smart, fast, and do well the job.
Give them i trial, they need a bit highter skill, but are very nice for nearby hauling jobs. Outside jobs, i use wargs or bears.

But i saw problems with bigger animals, such as Muffalos. They never ever could enter doors, open, locked, or whatever. I had to remove doors, sometimes ever part of walls to make them enter the base. Simply was thinking they was to stupid to find the way, or have a way poorer pathfinding.

I used petdoors at the beginning, but forget about them now. Maybe i don't use enough "small animals" to make them worth. Yorky end in hats in my colonies, cats, well i don't own more than one mostly if ever. They're useless as vanilla version unfortunately, so if i want cats, i'm opting for some useful modded ones. Normal dogs, not sure if they count as small animals. And i don't tame boomies, rats, skirrels and that useless stuff.

Same issue. On a new door, having never toggled the lock function, a tamed muffalo can walk through it. After I lock and unlock, the muffalo can no longer enter the door unless it's held open. This may have something to do with the pet door toggle as the smaller animals are able to use the unlocked door fine.

Need more info tbh. During my playthrou I did not have any issue with big animals and unlocked doors.

Also having this issue, not sure what kind of info I can give. Minions from Rimworld of Magic have the same problem, if their dropoff is on the other side of an unlocked door they just pickup and drop the item until they expire.
Everything works fine if doors are left untouched but once I use Locks to stop slaves from escaping my base the problem starts.

Originally posted by Hazzer:

Need more info tbh. During my playthrou I did not have any issue with big animals and unlocked doors.

It happens only when you lock the door and assign specific pawns to that door. It happens regardless of the Pet door option being ticked or not.

Had the same problem with unlocked doors. Large animals would not go through some doors even when the door was unlocked. The issue is that once you unlock the door, the list of owners is not cleared automatically. You therefore need to do it manually: Select the door, right click on "Lock" icon at the bottom of the screen, a context menu will pop up. Select "Clear Owners". This fixed my problem. Any door without this option was never a problem.