Rekordbox - unexpected application error

3) rekordbox version: 4.2.5
4) Using LINK: No
5) Source Hard drive / Flash drive / SD card file system: NTFS
8) Is rekordbox crashing at all: Yes
8a) If crashing, is it resulting in: Unexpected application Error
9) Are you able to repeat / reproduce the problem:  Yes
9a) If yes, can you do it consistently: Yes
10) Does the problem occur with one specific song: No
I mixing with 2x CDJ-2000nxs2 and DJM-900nxs2