Several ratings firms are lowering grades on commercial-mortgage bonds linked to shopping malls and office towers at a time when the long and sluggish economic expansion is causing experts to wonder whether a recession is looming.

Delinquencies are rising in the $528B U.S. CMBS market, and ratings firms from DBRS Inc. to Kroll Bond Rating Agency recently lowered ratings on property bonds just a few years after grading them, Bloomberg reports. Experts said the similarities between the pre-crisis ratings business and today’s practices are partly to blame, as banks are still able to shop around for the firm that will give them the best ratings.

While ratings firms are just starting to revise gradings, investors were already skeptical two years ago. Prices on bonds rated from 2014 have dropped as investor confidence in the sector and the practice of ratings shopping steadily declines. Retail is the second-largest property type funded through CMBS loans, and weaknesses in the mall sector have already cost investors billions.