I like what Boost11_64 can do to beef up a wimpy track or bus, but lately I've been seeing RED in the meters. 

I use it sparingly in X1-64. I've tried setting the Limiter as low as -2.0dB; it used to stop clipping dead, but now I'm seeing peaks of several dBs. It even clips with very modest boost levels of only 1 or 2 dB. Is this a bug, or is there some explanation for this?

Thanks.

Is it last in your signal chain? Remember if you have it in the FX bin to make sure that the PC is pre bin. If you have it in the PC make sure there's nothing in the FX bin or the PC is set to post bin.

It is last in the signal chain in the FX bin. In some cases it's all I have in the FX bin for a track or stereo bus. Can you please explain what is PC?

Ok, I think PC is Pro Channel? I don't have anything in the PC enabled.

Something has got to be turning the overall levels up after the boost11 plug. Check your gain staging. IF you are putting it on a track... Is the input on the bus you are sending it to turned up? Where is the output on that but set to in terms of db? Is there an EQ after boost11 that you are using to boost up certain frequencies rather than cut the ones you don't want? Something is up. It may not even be that though. I have had times where I hear something clip... I have to solo tracks one by one, find the track that is guilty. But the meters don't show the clip? So then I have it playing and look through my plugs.. Eventually I find something for instance if I am running 2 compressors in a chain together. The make up gain setting (or output) of the 1st comp may overdrive the input of the 2nd comp. Keep looking. You'll find it!

Be sure that the FX bin is not bypassed.