Sturmey Archer 3 speed shifter stuck

Hi Folks

Helped needed

Have two sturmey Archer 3 speed shifters. Both have the same problem – I bought this new one because I thought it was a fault with the original. As you'll see, shifting down is smooth but trying to go up just gets locked and doesn't move. Needs to be wiggled about and pushed in to get it to change.

Any ideas how to resolve it? Just to clarify, problem happened when the cable is in and it's on the bike too.

Thanks in advance!