Can you post the lines that are logged when dropping the file from Windows Explorer? 
Mine are:

Debug [Main]: TrackDAO::getTrackId(): Track location not found in library: "/home/daniel/60.wav" 
Debug [Main]: SqlTransaction - Started new SQL database transaction on "MIXXX-1" 
Debug [Main]: GlobalTrackCache - Resolving track by canonical location "/home/daniel/60.wav" 
Debug [Main]: GlobalTrackCache - Cache miss - allocating track ["/home/daniel/60.wav" | "/home/daniel/60.wav" | -1] 
Debug [Main]: GlobalTrackCache - Cache miss - inserting new track into cache ["/home/daniel/60.wav" | "/home/daniel/60.wav" | -1] QObject(0x0)  
Debug [Main]: SoundSourceProxy - SoundSourceProvider "libsndfile" created a SoundSource for file "file:///home/daniel/60.wav" of type "wav" 
Debug [Main]: TagLib - No cover art: None or empty list of ID3v2 APIC frames 
Debug [Main]: SoundSourceProxy - Initializing track metadata and embedded cover art from file "file:///home/daniel/60.wav" 
Debug [Main]: SoundSourceProxy - Adding missing artist/title from file name "file:///home/daniel/60.wav" 
Debug [Main]: SoundSourceProxy - No embedded cover art found in file "file:///home/daniel/60.wav" 
Debug [Main]: TrackDAO: Adding track "/home/daniel/60.wav" 
Debug [Main]: SqlTransaction - Committed SQL database transaction on "MIXXX-1" 
Debug [Main]: BaseTrackCache(0x435d320) updateIndexWithQuery took 0 ms 
Debug [Main]: BaseTrackPlayerImpl::slotLoadTrack "[Channel1]" 
Debug [Thread (pooled)]: CoverArtCache - Guessing cover art for "/home/daniel/60.wav" 
Debug [Thread (pooled)]: SoundSourceProxy - SoundSourceProvider "libsndfile" created a SoundSource for file "file:///home/daniel/60.wav" of type "wav" 
Debug [Thread (pooled)]: TagLib - No cover art: None or empty list of ID3v2 APIC frames 
Debug [Thread (pooled)]: CoverArtUtils::guessCover didn't find art  "CoverInfo(NONE,GUESSED,,0x0,/home/daniel/60.wav,)" 
Debug [CachingReaderWorker 1]: SoundSourceProxy - SoundSourceProvider "libsndfile" created a SoundSource for file "file:///home/daniel/60.wav" of type "wav" 
Debug [CachingReaderWorker 1]: SoundSourceProxy - Opening file "file:///home/daniel/60.wav" with provider "libsndfile" using mode Strict 
Debug [Main]: BaseTrackPlayerImpl::slotTrackLoaded 
Debug [AnalyzerQueue 1]: AnalyzerQueue - Analyzing "60" "/home/daniel/60.wav" 
Debug [Main]: WCoverArt::slotCoverFound WCoverArt(0xabde930, name = "DeckCoverArt")  "CoverInfoRelative(NONE,GUESSED,,0x0)" QSize(0, 0) 
Debug [AnalyzerQueue 1]: SoundSourceProxy - SoundSourceProvider "libsndfile" created a SoundSource for file "file:///home/daniel/60.wav" of type "wav" 
Debug [AnalyzerQueue 1]: SoundSourceProxy - Opening file "file:///home/daniel/60.wav" with provider "libsndfile" using mode Strict 
Debug [Main]: WSpinny::slotCoverFound WSpinny(0xc7a5050)  "CoverInfoRelative(NONE,GUESSED,,0x0)" QSize(0, 0) 
Debug [AnalyzerQueue 1]: AnalysisDAO fetched 0 analyses, 0 bytes for track 2232 in 0 ms 
Debug [AnalyzerQueue 1]: VampAnalyzer BlockSize:  1024 
Debug [AnalyzerQueue 1]: VampAnalyzer StepSize:  512 
Debug [AnalyzerQueue 1]: Beat calculation started with plugin "qm-tempotracker:0" 
Debug [AnalyzerQueue 1]: VampAnalyzer BlockSize:  32768 
Debug [AnalyzerQueue 1]: VampAnalyzer StepSize:  32768 
Debug [AnalyzerQueue 1]: Key calculation started with plugin "qm-keydetector:2" 
Debug [AnalyzerQueue 1]: Writing waveform from byte array: dataSize 26462 allSignalSize 26462 visualSampleRate 441 audioVisualRatio 100 
Debug [AnalyzerQueue 1]: AnalysisDAO saved analysis 453 "260232 (1909 compressed)" bytes for track 2232 in 10 ms 
Debug [AnalyzerQueue 1]: Saved waveform analysis for trackId 2232 analysisId 453 
Debug [AnalyzerQueue 1]: Writing waveform from byte array: dataSize 3842 allSignalSize 3842 visualSampleRate 64 audioVisualRatio 689.062 
Debug [AnalyzerQueue 1]: AnalysisDAO saved analysis 454 "38478 (495 compressed)" bytes for track 2232 in 6 ms 
Debug [AnalyzerQueue 1]: Saved waveform summary analysis for trackId 2232 analysisId 454 
Debug [AnalyzerQueue 1]: AnalyzerWaveform - Waveform generation for track 2232 done 0 s 
Debug [AnalyzerQueue 1]: ReplayGain 2.0 (libebur128) result is -12.4752 dB for "/home/daniel/60.wav" 
Debug [AnalyzerQueue 1]: Beat Calculation complete 
Debug [AnalyzerQueue 1]: Key Detection complete 
Debug [AnalyzerQueue 1]: Key Histogram 
Debug [AnalyzerQueue 1]: 2 : "D♭" 1.323e+06