aaronraimist and others that have encountered a UI "freeze" after bootup and login to desktop: I seem to have resolved my problem by uninstalling Dropbox (deleting Dropbox.app) and re-installing it.
(EDIT: I think I also had to manually delete Dropbox from the System Preferences-->Security&Privacy-->Privacy pane.)
I started getting this problem after installing Mojave's Security Update 2020-004, and it also occurred with Security Update 2020-005.
After bootup and initial login (and I think periodically about every hour after that) the User Interface would stop responding to mouse clicks and keyboard input for a minute or so -- then suddenly process all the input. The timing was associated with repeated messages in the /var/log/system.log file about the com.apple.tcc.system process:
Aug 25 14:17:03 imac com.apple.xpc.launchd[1] (com.apple.tccd.system[3708]): Service exited due to SIGABRT
Aug 25 14:17:03 imac com.apple.xpc.launchd[1] (com.apple.tccd.system): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
At the same date and time there would be crash reports with names like "tccd_2020-09-26-180449_imac.crash" in Console.app-->System Reports, showing crash information for the tccd process.
On my system, tccd would crash, be respawned, and crash again, seven times in a row within a minute's time. Apparently this repeated crash/respawn cycle was causing the UI freezes. I could reproduce the issue by just rebooting and logging in again: within a minute of logging in, a new freeze would happen along with the above mentioned messages and seven new crash logs.
The tccd process is for Transparency Consent and Control. It has to do with items in the Privacy tab of the Security & Privacy System Preferences pane (
according to this article).
I tried a lot of things to prevent these UI freezes/tccd crashes, but what seems to have worked (other than rolling back the security updates) was uninstalling Dropbox.app, verifying that the freezes no longer occurred, and then re-installing Dropbox. I had previously checked my Dropbox version and it was up to date -- at least, so I thought at the time. Perhaps I was mistaken.
I am
almost certain that my old installation of dropbox had a user "launch agent" (in ~/Library/LaunchAgents/com.dropbox.DropboxMacUpdate.agent.plist) to run "DropboxMacUpdate" every hour (3625 seconds) -- but now I see in my new installation that the launch agent .plist file is no longer there. I suspect that the running of the launch agent at login and every hour was causing the tccd process crashes.
Hope this helps someone else.