a few things to check because this has changed and newer devices like the RX3 and Opus can read 1000+ in a playlist (used to be a limit of RB and devices, NOT the hard drive or flash drive)
1. what version of RB are you on? update to 6/8/1 and try again
2. make sure you are in export mode and try this
let it sync and see if the 1000+ playlist still syncs even though you get the message that it may not


