Rekordbox 4.0.5 - What's changed?

Setup:

Macbook pro running 10.10.5 Yosemite

Pioneer XDJ-RX firmware 1.80

Pro Link via ethenet

Hi, I use Rekordbox live in the club as my sets are varied and it isn't feasible to export tracks to Usb devices. This has proven very reliable until last week when I  upgraded to version 4.0.5. The current version catastrophically crashes when clicking certain tracks in the collection. The program will instantly close and the active link will freeze meaning I cannot select music even from backup USB devices plugged directly into the XDJ-RX. Sometimes I get an emergency loop sometimes the music simply cuts off - this is very frustrating in the clubs!

I have managed to identify one of the tracks that causes this problem back at home. The problem occurs with or without an active link. The track in question I have had since August and have played it every weekend without problems. Rekordbox 3 which I still have installed has no problems with the same track, neither did earlier versions of Rekordbox 4.

So what's changed in version 4.0.5?

I have been able to delete the track from my collection using RB 3 and re-import it using RB 4 and it now behaves fine, but I have lost confidence in the software now. How many other tracks could potentially have this problem which is only applicable to 4.0.5!?