Guaranteed rent mismanagement?

Hello, My sister gave a property to an agent via guaranteed rent. They are up to date with the payments.

After viewing the property, I could see that it was in a state of disrepair. There was a leak in the ceiling and the agent claimed to have fixed and sent a bill to say that they had.

After getting a similar bill to the previous one it was apparent that the problem had not been fixed and when I went there I was told by the tenant that they had been trying to contact the agent to get the problem resolved for months without it getting fixed.

There were other things like the bathroom tiles taken off because they needed to find a leak but the floor in the bath was never fixed and at present there is just cracked cement in the bathroom, along with no actual bathroom door.

My sister has no trust in this company and would like her property back. I know it’s for a 5 year deal but if it’s proven that the company managing the property is negligent and by not dealing with problems to the house straight away it which causes bigger problems and more expensive bills, can she get her property back?

I know that they have a tenant from the council in the house and would assume they have some sort of agreement in place with them but getting charged to fix things, claim you’ve fixed them and then charging for it to be fixed again surely is grounds to have them removed?

Any advice would be helpful.

Thanks.

Ian