As before please try solutions given in similar thread. Or read below.
On clean installation of Ubuntu 18.04 LTS I do not have any issues with Dropbox and Caja.
You can try to do the following:
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Remove Caja-Dropbox from the system
caja-dropbox stop rm -rf ~/.dropbox ~/.dropbox-dist sudo apt-get purge caja-dropbox sudo apt-get autoremove
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Install Caja-Dropbox again
sudo apt-get update sudo apt-get install caja-dropbox
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Init Caja Dropbox
caja -q caja-dropbox start -i caja-dropbox autostart y