Comparator pulse extenders that use command blocks in the circuitry do not extend a redstone signal. As soon as the power souce is turned off, so does the circuit. If the exact same circuit is built, and the command block is repaced with a different solid block, the pulse extender works as intended. Since command blocks are also solid blocks, it makes no sense as to why they're an exception. If this is working as intended, please change this.