Mac – chmod using 100% CPU resources

Since upgrading to High Sierra (now at 10.13.6) on my Mac Pro 2012, I experience regular episodes where the process chmod eats up ~100% on all 12 cores.
It happens about 15 seconds after logging in and lasts for about a minute. It then happens again later while I'm working. Of course, the computer is quite unresponsive while it lasts.
In Activity Monitor I can see 12 instances of chmod using up each core.

I haven't been able to find anything with Google regarding this issue.

Can anyone help – any ideas?

System:
Mac Pro 5,1
48 GB RAM
2 x 3,06 GHz 6-core Intel Xeon
MacOS 10.13.6

EDIT: Having repeated boot/login while looking in Activity Monitor each time the number of chmod processes vary from 6 to 12, and other processes are (of course) also using CPU. I may have overestimated chmod usage by about 30%, the rest of CPU resources being used by the remaining processes – sorry about that. The problem remains, though.

EDIT: This is the list of entries from launchctl list that do not begin with com.apple:

620 0   com.adobe.PDApp.AAMUpdatesNotifier.5964.3198F160-6F8E-4D56-84B0-E905086713D0  
628 0   com.company.BackgroundScheduler.9044  
-   0   com.rogueamoeba.loopbackd  
593 0   de.rme-audio.RMEfirefaceUSBAgent  
616 0   com.leapmotion.Leap-Motion.5968  
-   0   label.9ZTHPRB4MV.com.soundradix.TTLWrapperAgent  
668 0   com.avid.ApplicationManagerHelper.5960  
603 0   com.acapelagroup.InfovoxiVoxUpdater  
604 0   com.avid.applicationmanager  
-   0   com.openssh.ssh-agent  
-   0   label.9ZTHPRB4MV.com.soundradix.TTLWrapperAgent.SL  
622 0   com.rogueamoeba.ScheduleHelper.9032  
-   78  com.paragon-software.ExtFS.fsnotifyagent  
595 0   de.rme-audio.firefaceAgent  
598 0   com.code42.menubar  
623 0   com.native-instruments.NIHostIntegrationAgent.5976  
629 0   com.abyssoft.teleport.5972  
-   0   com.adobe.AAM.Scheduler-1.0  
-   0   com.oracle.java.Java-Updater  
-   0   com.iconfactory.iPulse.5996  
-   0   com.paragon.updater  
601 0   com.spotify.webhelper  
615 0   jp.plentycom.boa.SteerMouse.9028  
583 0   com.prosofteng.DGMonitor  
-   0   com.Arturia.ArturiaSoftwareCenterAgent  
-   0   com.google.keystone.user.agent  
-   0   com.leapmotion.Leap-Motion