Non-completion agent fee

Hello,
I've received a contract with the following and it does not seem right to include the word "inability".
I don't particularly like the whole clause but that word in particular seems off to include. Also, what is a normal fee to pay an agent if you back out of an agreement? Any thoughts would be appreciated.

"If the non-completion of the sale is caused by the Owner of the property or the sale is not completed on account of the Owner's refusal or inability to perform, or in the event that this Agreement is cancelled by the Owner for any reason other than the default on the part of the Agent or the sale of the property through a third party, the Owner shall pay the Agent a fee of two and a half percent (2.5%) of the listing price"