Spoke to Apple. The issue is with High Sierra’s new file structure not allowing the files up to 4gb to be copied. They say they are working on the issue and the fix will come out in a later update.
In the meantime, they gave me 2 workarounds: 1 ) bump back down to regular Sierra, which requires backing up everything and reinstalling Sierra from scratch (No bueno) and 2) using the Terminal to transfer files (much easier).
To transfer via Terminal in MAC High Sierra: Open terminal and type “cp<space>” then click and drag the file you want to copy into the terminal window. Then click and drag the destination (the flash drive) onto the terminal widnow. There will be no progress indicator to alert you that anything is happening. The only way I knew was to look at the destinaltion and watch file grow in size periodically. Remember, the FAT32 file structure still has the 4gb file size limit, but at least this will work until they fix it in the system software.
Also, if you wnat to copy multiple files, place them in a folder and click and drag the folder instead of the single file to copy.
Hope this helps.