Tenant Will not allow inspection during due diligence phase

[Austin Sroczynski]

I have a duplex under contract and have had smooth sailing until the tenant of one side of the duplex will not allow anyone (inspector, owner, or me) into the unit until next Thursday. Currently the tenant does not have a  written lease with the current owner and the current owner is too timid to stand up and give them 48hour notice. I have not seen the unit and am not able to get an inspection done for at least another week. I feel like the tenants are trying to hide something but I'm not sure. If you were in this situation, what would you do? I was thinking about changing my offer based which would hedge myself against an eviction and vacancy over winter. (8-10K reduced offer) I'm not sure if I should continue or not. Any and all advice is welcome.