Commercial mortgage-backed securities have performed relatively well over the past two months, but a few major loan losses highlighted some of the potential risks in the sector, Trepp Analytics said.

First, there was the troubled $39 million Washington Mutual Buildings loan.

When JPMorgan (JPM) acquired Washington Mutual in 2009, it rejected leases on two properties backing the loan. The loan prior to August represented 4% of the collateral behind the GECMC 2005 C-1 CMBS transaction.

The note is backed by two offices in Los Angeles. The properties together had an appraisal value of $63.5 million in 2004, but by mid-2009, the value was reduced to $15.8 million.

On Friday, investors learned the loan was resolved with a 177% loss, Trepp reported in TreppWire.  The steep loss wiped out five classes of bonds (GECMC 2005-C1 tranches J-N). In addition, 35% of the H tranche was wiped out.

The West Hartford Portfolio loan, which made up 2.1% of the BACM 2007-5 deal, also was resolved with an 89% loss, with five classes of bonds eliminated. That particular note was backed by 23 multifamily properties in Hartford, Conn.

The loan previously had an appraisal value reduction of about $22.5 million, but the real loss ended up being far greater, Trepp said. The portfolio pulled in $10.4 million, which was reduced to $3.8 million due to liquidation expenses.