Thunar hangs for several seconds on first launch

Is this bug specific to a view (icon, detailed, list) or side pane view (shortcuts, tree)? Do you maybe have bookmarks to remote locations, or (broken) symbolic links in your home folder?

No broken links, remote locations are instantly reachable (confirmed by doing an ls from a command line prior to the operations).

I am just trying to open a folder contained within the Desktop folder by double-clicking the icon. Thunar will start running instantly (the process will be created), but nothing will happen visually for ca. 15 seconds. As previously stated, during this time there is no unusual CPU load or network load.
Eventually, the window will show, but after that, Thunar will go back to being unresponsive for ca. 15 seconds more before anything within that window can be selected or opened. During that 15 seconds, again, there is no unusual CPU load or network traffic.

The Xfce session starts Thunar as daemon process which provides a D-Bus interface for various file manager actions.

Is this process created for you? Does killing any running Thunar process (thunar -q) and opening the folder again trigger the bug too?

I see a Thunar process for the directory in question:
ps ax | grep -i thun
 230091 ? Sl 0:00 /usr/bin/Thunar file:///home/<redacted>/Desktop/<redacted>

Which is created immediately when I click on the icon. After the delay, the window appears (but is unresponsive). At that time I still only have the one Thunar process. After another delay, the window becomes responsive (still only one process).
At this point, I can click on other icons on the desktop and get a window immediately (still only one process), but the windows are unresponsive for the same delay.
Closing all windows, shutting down Thunar, and re-running puts me back to the beginning state of no window for a delay, and then unresponsive for a delay.

This may be a layer under Thunar - I just notice I am getting the same sort of delay when I have Firefox try to save something - a long delay before the save dialog shows up.

OK, I found the source of the problem - trash ibus files, some owned by root, that was causing issues with Thunar's communications.

For others: If you see this, remove ~/.config/ibus, ~/.cache/ibus, and ~/.dbus and reboot.

Now, how those bogus files came into being... I have no idea.