The new base azimuth lock lever, comparing to old one, was very tight that i had no way to loose or lock it. Not sure it is designed this way or this particular one is over tightened.
The azimuth lock in my new RST-135 was *very* tight too (don't know about the new base for my old RST-135 -- I haven't opened the box yet). When the new RST-135 arrived, it appeared to be stuck at just perhaps 20 to 30 degrees from one end.
If your lever is not completely all the way on one end, you should be able to loosen it too. Just remember to turn it in the correct direction (:-) or you will be tightening it even more!
When you look at the mount assembly from above, you turn the azimuth lock lever counterclockwise to loosen it. A photo with an arrow to show the unlock position appears I believe in the original RST-135 manual.
I had to sort of lightly tap the azimuth tightening lever with a screwdriver handle plus copious amount of rags to provide more protective padding to get mine to loosen up. I am too weak to just push with my thumbs. Again, be sure to tap in the correct direction! :-)
Edited by w7ay, 24 May 2020 - 05:10 PM.