I am seeing this problem in March of 2021. I click to start a line, drag it a little, enter a specific length, then the line locks where the mouse was and no amount of changing the length value changes the length of the line. I have to either press ESC to clear out and start over, or I have to click to place the endpoint and then dimension the line. It's irritating to say the least. It just started doing this on a design I've been working on for a few weeks.
Seems silly to set the compatibility property to "Windows 7" on Windows 10. I have a fairly new machine: AMD Ryzen 9 Threadripper 16-core, 64 GB of RAM, NVIDIA RTX 2080Ti with 11 GB. I've never experienced this problem until tonight. Fusion 360 did update itself this earlier today.
I can't find any preferences or any settings that cause it or fix it. It's random. This needs to be resurrected. It isn't normal behavior.