That’s because the “volume check” during an LLD step is checking the found height and comparing it to the distance that it must travel. If the found height is less than the distance it needs to move during the aspirate step, then it flags an insufficient liquid error. If you use the step return on the aspirate, you would only get a return of heights.
You’d need a separate function such as the DevComputeContainervolume from the HSLDev library (shown in the example method I shared above). Given some of the inherent limitations in the Hamilton labware editor, you could only get an estimate of the volume so if that isn’t accurate enough for your purposes, there are other options. For example, with the returned height, you could compare the value to a separate lookup table where you have a list of heights and known volume for each height that you measured.