Sounds a bit suspicious to me, I suspect they have something to hide and don’t want to be making changes to cover up their breach of your contract, e.g. an unauthorised pet, additional resident, drug dealing or even running a cannabis farm.
Just explain you are making an inspection of the property, not the way they live. It’s irrelevant if they have a sink full of dirty dishes and are not tidy, as long as their lifestyle is not detrimental to the property, e.g. causing damage or mould.
Of course you need to abide by your TA’s T&C”s in respect to the periods of inspections.
An alternative approach could be to speak to your electrician and ask him to take photos of the electrical installation and have a personal chat with him before and after he finishes his work to see if he’s noticed anything untoward. That way you could learn something without the tenant being aware of your vigilance.
Another possible approach is to install CCTV externally, with a remote viewing app, which would identify the comings and goings.
I’m currently trying to gain possession following an ignored S21 from a tenant who’s Father (guarantor) pays his rent while he doesn’t work, receives UC and contributes nothing, but he managed to buy a brand new car last year. You don’t need to be Einstein to work that one out, he’s obviously up to no good, which has been reinforced by the visits from police and threatening notes stuck to his post box from undesirable acquaintances. The police have even been and broken the door down costing me over £300 to fix as they deemed it a legally entitled entry using necessary force, so are not liable for repairs. What an ass the law is!
You certainly don’t want it to get that far whilst you still have the option of an S21.