During the tube times many electronic devices tended to drift away from precise tuning point - I still remember our table radio, which needed some re-tuning at some intervals. They had to develop AFC ciruits to keep things spot-on. And then came the transistors, which should be insensitive to heat...Btw, my analog transistor tuner still has an AFC. The digital devices should be better, but even the quartz oscillators drift because of heat - the better wrist watches do have a temperature compensation circuit. Some A1200s are more susceptible to heat than others, developing GFX glitches. And external scandoublers are housed in very tiny packages, developing drift when warming up - hence many of them have trim pots.
