I tried to explain what you are doing wrong. Even on the old firmware, this is incorrect.
Yes, it works if you pause between command and data retrieval.
Even on the old firmware, it is necessary to use the sequence of commands that I gave.
Again, the sweep command will only set the start and end frequencies on the device. Then the device must make at least one pass (if there is no pause). The date command returns the current data value. If you set the interval, and immediately request the data, then you will get the old dataset.
On this I will no longer recommend anything, do as you want