My opinion
I'm not a gunsmith, but I have some experience working with metal. In my humble opinion, one cannot afford to let an assembly pin walk, even ONCE. Especially if more rounds are fired after it walks, i.e. before it's shoved back into place.
Wildames says there is already frame wear on the right side of the frame. That also means there is probably some wear on the left side, it's just not as visable.
No matter how hard it's alloyed, there is no contest between aluminum and steel. Steel will eventually win every time. Even if the defective assembly pin is replaced now, the new pin will not be fully supported on the right side in the future due to the existing frame wear. This, in my opinion, will eventually lead to more problems.
That's why I'm so concerned not to EVER let my assembly pin walk, even once. In a rapid fire string it might walk on the first shot and I might not notice the problem until the end of the string, Hence yzguy's grove and screwdriver slot are in order, or at least one of the new style pins even if your pin has never walked before. Ten bucks is cheap insurance. Just my opinion.
Keep shooting