As I mentioned in another thread, I do not have issues with the lever of my Uberti Walker dropping down during firing, even with full chamber loads.
I bought my revolver in about 1975 as Uberti's cased Walker with accessories. It has a very low serial number. Upon firing, I found the lever dropped down and had to be continuously snapped back up to fire the next chamber. I didn't know at the time that this was a common fault. But it wouldn't do so I fixed it.
If I can remember correctly, I increased the tension of the latch spring by simply bending it toward the muzzle just a few 'thou'. With the lever up and latched, I could see that the case hardened lever was simply resting against a curved surface, relying completely upon spring tension to do the work. So I used a sharp needle pointed scribe to mark the spring with the latch closed tightly, then released the lever, and gently and accurately, filed a tiny flat notch in the spring to act as a catch for the lever. I hit it perfectly with the first 'go' and I've never had any trouble with it since. I'll ionclude a couple of photos to further help explain this.
This image is of the lever hard up against the barrel and held by the latch.
And this one shows the bulbous end of the spring with the tiny notch filed into it. This last one is a better image of the fix.