Unethical agents

The market in San Diego has been heating up lately. Some areas are having bidding wars. Our office encountered some cases where, the buyers' agents, in order to get sellers to accept their offers, would say in the contract that their buyers are going conventional financing. After sellers accept their offers, they would then switch to FHA financing without the sellers knowing...until it is too late. Deals end up not closing because property cannot appraise, or deals are delayed for weeks.

Unfortunately for the sellers, the other offers that were on the table were long gone...

I wonder if this is a common problem? Has this happen to you?