false step
1. Literally, a misstep or stumble while one is walking. I took a false step on the mountain path and nearly went tumbling over a cliff!
2. By extension, an unwise, miscalculated, or blundering act or decision. We made a few false steps while setting up our business that nearly ruined our endeavor altogether. It seems now that the president's decision might have been something of a false step.
false step
A stumble or blunder, as in Making a down payment without securing a mortgage was clearly a false step. This term transfers physical stumbling or tripping to other enterprises. [c. 1700]