I found a solution to the problem of searching for invalid file name characters on Dropbox. The reason for the problem is that certain characters (like ":") are not allowed in Windows file names. Dropbox search does not support searching for ":".
The solution -- use a Linux based File manager. I used the Synology Filestation program (Synology NAS runs on Linux), and mounted Dropbox. Synology's search will find files with ":". It can also move all of the files that you find to another directory of your choosing. This solves the problem with the Dropbox utility (bad names check) that crashes Windows PCs ) I guess the problem with this solution is you need a Synology NAS device.
Not very clean, but from what I can see, this may be the first solution to Dropbox search problem for invalid Windows filenames. As an aside, you can solve the bulk rename problem, with another 3rd party program, Winzip.
