The character in the 1st image you sent doesn’t seem to be in-game, it looks like he’s in the viewport of the anim BP or the anim viewer. Only when he is in-game, and with the gun in his hands, the positions of the gun sights are calculated (CalcSightsTransforms) and sent to the anim BP. If I look at my character aiming in the anim BP viewport, I get a similar result to yours:
So don’t forget to bring CalcSightsTransforms to your gun BP (and call it when the gun is attached to your character’s hand) and test your character in-game. If you’re getting similar results in-game, there could be something missing in the CalcSightsTransforms implementation.
I haven’t tried yet to apply the Gun Sight Aligner to the ALS character (will probably try it when I have some time), but I believe it should be possible.