There is enough space on the server and Attach does exist, there is no sample.txt in the Attach folder. However I can see there is a .txt file (which should have to be imported) in the Attach folder which is not renamed to the UUID.
The same file has been imported earlier than the modified date (17:02) of that .txt file

2017-05-03 16:40:44 NM CheckInternetEnabler failed
2017-05-03 16:40:46 JU/THREAD(14) Ataskaita Prekių likučiai
2017-05-03 16:40:47 JU/THREAD(14) 1 running reports, duration for InvValRn was 0.61 seconds, of which 0.00 was used in 0 steps
2017-05-03 16:41:01 NM Database set to unsafe (import and maintenance) mode
2017-05-03 16:41:01 NM Imported 0.82 percent/6493 RLinks in the database
2017-05-03 16:41:01 NM EndAppImport

2017-05-03 16:41:01 NM Flushing
2017-05-03 16:41:01 NM Database set to safe (normal) mode, flushing cache...
2017-05-03 16:41:02 NM ... cache flushed
2017-05-03 16:41:02 NM end of import
2017-05-03 16:41:02 NM Duration in seconds: 0
2017-05-03 16:41:02 NM Byla importuota apjungtos_2017-05-03_16_39.txt << this file is in the Attach folder with modified date 2017-05-03 17:02
2017-05-03 16:41:02 NM Duration in seconds: 0
2017-05-03 16:41:05 NM Database set to unsafe (import and maintenance) mode
2017-05-03 16:41:05 NM EndAppImport

2017-05-03 16:41:05 NM Flushing
2017-05-03 16:41:05 NM Database set to safe (normal) mode, flushing cache...
2017-05-03 16:41:05 NM ... cache flushed
2017-05-03 16:41:05 NM end of import

version 8.3 2017-03-19 (build 83250401)