The TARDIS' inappropriate changing appearances where deliberate on the TARDIS' part.
Obviously in this episode the TARDIS the Doctor finally repairs the Chameleon circuit, only for it to keep choosing objects that
don't blend in, very well and the new shapes were far harder to get in and out of. It's assumed it's still faulty, the TARDIS resets to the classic police box look and locks again at the end. However there is another possibility. We know in [[/
Doctor Who S32 E4 "The Doctor's Wife" The Doctor's Wife]] that the instances where the Doctor lands in the wrong place and/or time, are actually the TARDIS taking control and putting the Doctor when it knows they need to be. If the TARDIS can usurp control of it's primary function from the pilot then it can be assumed it can control automatic systems like the Chameleon circuit. It stands to reason that the TARDIS has grown attached to it's police box appearance, and deliberately chose outer shells that were as inappropriate as the Police Box in terms of camouflage and harder to enter and exit, in order to irritate the Doctor so that either he'd purposefully disable it again on just give up when it breaks again.
Alternatively to just wanting to look like a Police Box, the Doctor Who Magazine story ''Hunters of the Burning Stone reveals that the reason the circuit fails in the first place is the 11th Doctor returning to the scrapyard to deliberately lock the TARDIS into it's Police Box form in order to create a symbol of hope for humanity, and the universe at large, in no small part because he needs one to counter the antagonist's plot. If the TARDIS know's that it's outer shell is supposed to serve this purpose then it would be trying to stop the Doctor from disrupting a mission he himself is going to have given it.
A third possible motive would be that The Doctor's Wife states that the TARDIS isn't bound to it's own timeline in a linear fashion like the Doctor is, having archived multiple console rooms that the Doctor hasn't used in the present yet, if it knows what it's insides are going to look like in the future, then it stands to reason it'd also know what it's outsides are going to look like and so it knows it's meant to look like a police box and just needs to annoy the Doctor into not trying to change that.
