Rekordbox 5.+ lag

Hello.

I have problems since rekordbox 5.0 and updates was installed- in export mode while scrolling, searching or exporting track to player rekordbox freezes for a shorter or longer time and after that load track to player or sometimes crashes (playback goes normally but rekordbox itself needs to be restarted).
Macbook air 13” mid 2011 i5 4GB RAM, 256 SSD + apple USB-RJ45 plug.
2x CDJ2000 nxs2 + DJM900nxs2 + 8ch LAN switch.

Earlier there was No problem with rekordbox 4.+.