How do I catch quality problems when the volume is overwhelming?

You catch most of the quality issues now, but under the flood of volume the subtle ones still slip past. That is honest, and it is not a sign you are slipping. When the count is high and the pace never lets up, the eye tires and the small stuff hides in the sheer number of things moving past you. You will not beat the volume with willpower; there is simply too much of it. What works is a sharper focus. You cannot inspect everything equally, so learn where the problems actually cluster, which items, which sources, which moments in the flow, and spend your attention there. A trained routine aimed at the likely trouble spots catches far more than an even, exhausted glance at everything. Look back at the issues that slipped through lately and find the pattern in them, then build a quick focused check for that pattern into your flow. Aim your attention instead of spreading it thin. Under high volume, the win comes not from seeing more but from seeing the right things on purpose.