When recording in loop mode in Studio One with input quantize disabled, you probably experienced the following issue once in a while.
The note(s) you play, intended to land at the start of the loop (left locator) end up at the entire end of the loop (right locator), because you played them a few milliseconds early.
This can be solved by adding an adjustable MIDI catch range. Which basically is a hidden zone with adjustable length (in millisecond) at the right locator (end of the loop). Any notes played within the zone (intended to land at the start) will be placed at the left locator (start of the loop)