Input Pregain 'hiccup'?

So I’m automating the pregain to change overall track volume without messing with my automation. Every now and again when the pregain cuts in (the little bar goes a brown colour and the pre light goes on) the sound will hiccup, as if the gain is suddenly dropping then returning to proper value. But when I play it back again it’s fine and nothing happens.

I’d say it happens once in every 4/5 times. Checked the cpu meter and there’s no spikes there. Only workaround I’ve found is to have the default pre gain value at -0.1, so that it’s activated all the time.

Is this a bug or am I just using the pregain incorrectly?