There are several cable types on the market which use a jacket material which is soft and spongy, claiming ultra flexibility. The DXE-UT-8213 cutter blades are designed to cut through the more rigid materials encountered with quality RG-213/U, LMR-400 and similar PVC and PE jacketed cables.
The soft jacket materials are sometimes described as "thermoplastic elastomer" (found in LMR-400UF Ultraflex) and are characterized by their ability to be stretched and twisted free from the shield braid. As a result, the cutter blade will twist the jacket and cutting action will stop, jamming the tool. These unusually soft-jacket cables need to be stripped the old fashioned way.