What' your audio interface, buffer settings?

Thanks for your reply. I'm using a Steinberg ur44 for my interface. All my buffering settings are set to default. Media buffer size 1200 ms 100% prebuffer auto-detect the number of needed audio processing threads is activated disable media buffering for tracks with open MIDI editors is activated anticipate FX processing is activated render ahead 200 ms use native events for synchronizing is activated

Would it make any difference if I were to update to macOS Sierra? Thanks

The request block size is set to 512, however the box isn't activated. Same goes for the request sample rate. It's set at 48000, but not activated. Should I activate these boxes? Another odd thing is Reaper is running fine today, no glitches so far. I'll continue to monitor it to see how it goes

Thanks for the replies. Been working masters today and still no glitches. I've stacked a bunch of plugins, and done a quite a bit of real time adjustments . The hard drive in this machine has been updated to a 250 Gb solid state drive. The glitching I was experiencing yesterday was when I was working with 2 track masters. Using some Reaper plugins (ReaXcomp, ReaEQ), some limiter plug ins (isotope, Limiter #6), and a few others. Some were AU format, others VSTs, or VST3s. The glitching happened no matter which plugs I had running. I even removed them all, and still had the problem. I've never viewed the activity monitor. Thanks for that suggestion, next time the problem occurs I'll check that out. The Steinberg ur44 came with it's own drivers. Thanks for the info. I'm wondering if maybe there is an issue with this laptop. Running great today. Yesterday when the Reaper problem was going on, the computer was running sluggish in general. Didn't have any other programs running or any scans going on i the background that I was aware of.

Thanks for that explanation. I'll check the boxes. Seems like I'd rather have Reaper taking care of that monitoring. Should I keep the sample rate at 48000? Also, what is live sample rate conversion?

Thanks for the info. I checked my Reaper preferences>options>device on my pc, and found I had the sample rate set to 44.1. Went ahead and switched it to that in my mac as well. Thanks again for all the help and suggestions. I'll post again if the problem returns and I'm able to track it down.

Well, I think I have found what's causing the glitching. When I use any combination of ozone plugins, or the wavesL3-16 plugin, it all starts. My cpu usage was floating around 15% to around 20% at most when the glitches occurred. Does anyone out there use the isotope ozone7 plugins, or the Waves L3-16 on a comparable machine? This is running on a 2011 MacBook Pro OX 10.10.5 with a 2.0 processor, 256 solid state drive, and 16 Gb of RAM. Thanks

Thanks for your suggestions. Little while ago Reaper was running fine. Had 2 ozone plugins running (maximizer & vintage limiter). Was able to make real time adjustments to the setting with no problems. Now when I open the same track (2 track) with the same effects as before, the song is barely reconizable thru all of the clips. I tried adjusting the request block size to no avail. Even disabled wireless and spotlight to try to free up some space. Is there a reason this problem could be so intermittent ? Can't figure out why it runs so clean sometimes. Tried restarting Reaper and restarting the mac as well with no luck.

Just realized I was unclear about some of the details I gave. When I master my tracks, I render down the multi tracks, then open the rendered track as a new project. (So the rendered track is a new track). I apply all the mastering effects to the track instead of applying the effects to the master track. Is this something like "sub mastering" ? When a track, or effect, is frozen, is it rendered to a new waveform?