Yes try using mono on mono channel OR switch to whatever the  current interleave isn't if you know what I mean.   Do one UAD plug at a time as they all don't cause that behavior. ALSO, try moving the plugin from one channel to another and then back again.   I know these are weird solutions but at different times they work.

I keep my stereo & mono UAD plug-ins in separate folders for easy access and organization. The main reason I use the mono versions is they use less DSP (sometimes a lot less DSP) than simply using the stereo versions on mono tracks. A stereo tranny enabled FATSO used on a mono track uses the full 40.5% DSP @ 44.1k. Simply using the mono version reduces the DSP load to 25%. Less DSP use means more available DSP for other plug-ins. Most of my tracks are mono so the DSP savings can be significant.
In the SONAR Plugin Manager default VST list, the top UAD plug-in is the mono version and the bottom is stereo (even though they appear identical).
 
Cheers,
 
Billy Buck

Billy Buck
I keep my stereo & mono UAD plug-ins in separate folders for easy access and organization.
 
Cheers,
 
Billy Buck

I do this myself, along with deleting the plugins I do not own (within the vst folder, but keep a backup of that folder in case of new purchases). IIRC, they install by default to mono and stereo folders.
All the best.

Billy Buck,
 
I use to do this with MONO instances as well, then I read some where on the official UA site that this issue was addressed by their software implementation and no longer need to use the MONO plugs.
 
If I a reading you correctly, this is not true and I should return to the MONO versions.  I did notice that if I used a MONO plug in certain FX chain combinations on a stereo track or a STEREO plug on a MONO track in the old days in SONAR, weirdness would happen and using the MONO plugin on a MONO track fixed the weirdness. Which got corrected after the UA update for this.
 
Not debating what you said, trying to learn from you on how to proceed going forward.
 
Thanks,
Jim

jimkleban
Billy Buck,
 
I use to do this with MONO instances as well, then I read some where on the official UA site that this issue was addressed by their software implementation and no longer need to use the MONO plugs.
 

 
Hey Jim,
            The latest versions of SONAR/UAD still use DSP according to the actual version used (stereo or mono)
on a particular track. Not sure of any other software implementation aspect being fixed, as I always use mono versions on mono tracks and stereo versions on stereo tracks. But the DSP savings is still applicable. I do the same thing in REAPER and Mixbus as well. Those two apps you do need to use the appropriate versions as there are other related performance issues, in addition to the DSP savings.
 
In the screen capture below, I have two mono tracks. The top one I inserted a stereo UA610 and the bottom one the applicable mono version. In the UAD Control Panel|Hardware pane you can see the stereo version is using the full "stereo" DSP load of 44.8% (DSP 1) on a mono track, while simply inserting the "mono" version the DSP drops down to 23% (DSP 2). That is reason enough for me to use the mono versions. In a project using dozens of UAD plug-ins, the DSP savings can be quite significant.
 

 
Cheers,
 
Billy Buck
 

Billy,
 
Thanks for the reply and information.  I will check this out again.  
 
Jim