Best laid plans and all.
My Mom and stepdad had wills where if one died, their kid(s) would get x amount from certain accounts already set aside as POD and a life policy. Surviving spouse gets the remaining assets (house, other life insurance, pension). Stepdad passes and my Mom learns he had changed the will and beneficiaries on the policies. So now my step-sisters get the POD accounts (as expected), but also all the insurance, his pensions, and half the house.
Mom ended up with the main joint account, and half the house (plus her retirement accts). Shortly after the funeral Mom's step-daughters start bugging her about their half of the house. Custom house, he died when the market is start to tank, so market value is probably $150k less than what the step-daughters thought they were getting out of it. Hilarity attorney talk ensues, they want money from Mom for the house, she wants to sell it but the price they want to sell it for is unreasonable. Lots of shitty conversations over the next few months until the house finally sells after several price drops.
Yadayadayada, Mom fucked up, she trusted my stepdad not to change his will behind her back. In the end, she is fine financially with her retirement, savings, and low COL. Just lots of initial shock, anger, and lessons learned. We no longer talk to the step-daughters or other family. Mom revised her will very shortly after. Fin.