Sounds like the OP’s son and ex started an assisted living facility business. The son and the ex also bought a building that was leased to the business. This building purchase appears to have been financed through a bank which included a mortgage on the building and real property. It also appears that this loan was guaranteed personally by both the OP’s son and his ex.
Since this business has started a few things have occurred. The son and the ex have split. The ex sold her shares in the business to the son. But it appears that the ex still owns half of the building, as she collects $4,200/mo. for her share of the rent. However the bank has not released the ex from the guaranty and his still personally on the hook for the loan amount if the value of the building and property are not sufficient to satisfy the loan amount, when due. The original loan is coming due and is being processed for renewal. The bank would like to get the personal guaranty renewed as well which includes both the son and the ex. The ex refuses to resign the guaranty, since she sold her shares in the business to the son, but it unclear if the ex sold her half interest in the building to the son. I don’t think so since she is still collecting $4,200/month in rent.
Son has now gone to Wells Fargo to see if they will re-finance the building, but they have said no.
I see less to blame Wells Fargo here, than the OP’s son.