Auto relocate doesn't work for every songs (RB 6)

Hello there!

I recently changed my laptop and I want to use Rekordbox on this new device (switched from PC to Mac). However, since I already have all my songs on an external hard drive, I simply exported the Rekordbox database from my old laptop (PC) to my new one (Mac) without the songs.

Everything's good so far but then, when I try to use the auto relocate tool, it works only approximately for 1500 songs out of my 2300 songs collection. I've looked a lot online and I can't find any solution to fix this. Many people say to go into Preferences > Auto Relocate Search Folders > and select the specified user folders where I want to relocate my tracks. Even when I do this, it still doesn't work. Also, it is worth mentioning that when I relocate the remaining missing tracks MANUALLY (one-by-one) it does work and I'm 100% positive that these songs are all in the same file as all the other songs that have been relocated successfully with the auto relocate option.

Does anyone know what's causing this and how to fix it?
Thanks in advance for your help!