What factors limit the accuracy, frequency response and stability of an oscilloscope?

An oscilloscope's overall performance is bounded by its internal circuitry, specifically the time base and the deflection amplifiers. The time base generates the sweep across the screen (X-axis, representing time). If the time base is inaccurate or unstable, any frequency or timing measurements you make will be wrong. Meanwhile, the vertical deflection amplifiers (Y-axis) dictate the instrument's frequency response (bandwidth) and amplitude accuracy (linearity). If an amplifier cannot linearly track high-speed voltage changes, the displayed waveform will be distorted or artificially reduced in size. Distractors mentioning 'tube face voltage increments' or 'output impedance' are either nonsensical terms in this context or refer to factors that do not define the fundamental limits of the scope's bandwidth and stability.