There’s several things what you need to check.
-The firmware on the card updated to 3865 firmware release.
-The USB drive must be formatted with uTrack-X32 card.
Very unlikely the playback has dropouts and the recording not. I assume the dropouts happened during the recording.
I suggest you to make a test recording on USB HDD (formatted with uTrack-X32) and check the status in uRemote. If any dropouts happens during recording it must be displayed in the application.