icdd high cpu when dropbox running

I have a M1 Mini with frequent restarts and crashes running Big Sur. Etrecheck says major problem is high cpu usage. Indeed the process ICDD is frequently over 90%. I ran the following tests:

Turned off wifi - ICDD usage went to zero

Quit all manually started apps - still 90%

Restart in safe mode - 3%

Restart normally and then kill all processes with Dropbox in name - 5% (was going to go through list of boot start items)

Saw issue about Dropbox using cpu if symlink or similar present. My Dropbox processes not taking excessive cpu but removed an alias which made no difference.

Both the wifi test and stop Dropbox test suggest that ICDD and Dropbox together with wifi result in excessive cpu usage

I also have a M1 iMac with much the same setup and it is well behaved. What to do now other than stop using Dropbox?