Analog Servo Only Turns if you start from value where you left off

Hello! I have made a post regarding servos in the past and I haven't been active since. Through my testing with a proper power source, both my MG995 and my Analog Rage rgrs142-16-6vm worked using the sweep sketch. But if I just give it random angle values, only the analog servo will not budge. It only works in sweep or using a potentiometer and it only moves when the values catch on to the number where I last left off. Also, rapid fluctuations in angle values cannot be read by the analog motor. So a fast sweep won't work. Is this a common occurrence? Thanks.

No. RC type servos always attempt to move to the commanded position as fast as they can. An "analog" servo doesn't have a lot of smarts inside that would prevent it from doing that.

What do you consider to be a 'proper power source'? It really must be a battery. Even a relatively beefy 2A plugpack can't keep up with the instantaneous demands of a servo. Can you measure the voltage directly at the servo terminals?