Rekordbox Cloud Sync prob - Collection updates but get "File is on a different computer" error

I've setup rekordbox Pro on 2 laptops, installed Dropbox on both and have logged into both with the same accounts.

Dropbox sync is working and when I drag a file into the dropbox Music folder on one Mac, it appears a minute later on the other one.

The problem I have is this. if I add something to the Collection on the second Mac, it appears on the first one and everything works perfectly.

But if I add something to the collection on the 1st mac, it appears in the Collection on the second one, but with a crossed out cloud next to it and when I mouseover I get error "This track is stored on another computer or mobile device"- But the track has correctly synced to Dropbox on the 2nd Mac.

If I look on the first Mac at Track Info > Summarythen it has a location of "Dropbox/RekordboxMusic/.... track name"

but if I look at the Track info for the same track in the collection of the 2nd Mac, it has a locatioon of "LucasMacBookPro/users/username/Dropbox/RekordboxMusic"...."

So it seems that it is specifcally pointing to the first Mac when it should be just starting with the Dropbox folder

Can anyone help?