Sonitus gate - strange issue

I opened an older project earlier to mix it. It was recorded in Sonar and I opened it in BL Cake. The first thing that I noticed when I started playing through, was some low-level audio artefacts very low in the mix. I started trying to find the cause. I soloed the vocal track and could still hear the intermittent noise. I then soloed another track and played a silent part of it. I could still hear the artefacts - they sounded like chopped up, very short bits of vocal. I then noticed that even with this track soloed, I was seeing meter activity in the backing vocal mix bus. That bus had 2 plugins in the bin. One was Sonitus gate, so I disabled the gate and the artefacts went away. Not sure what the issue was, but I deleted Sonitus gate and replaced it with another gate and all was fine after that. Anyone else had this?