I noticed some odd behavior when using gapped playback for audio on 18.0.158 (also verified on 180.0.174).
I usually set the gap to 2 or 3 seconds for DJing and noticed that the gaps between tracks sometimes seemed to be rather short. I tried experimenting today and set the gap to 10 seconds to make the problem more obvious.
I have mostly mp3 and flac audio files and found the following:
1) If the playlist moves from mp3-->mp3 or flac-->flac, the gap is heard and the length of the gap can be verified from the Remaining Time on the display which reaches zero at the end of the file and starts counting positive for the length of the gap.
If the playlist moves from mp3-->flac or flac-->mp3, the gap is ignored and play of the new track starts immediately after the previous track ends.
2) Another odd thing I noticed, that may be a part of this problem, is that when the gap works (e.g. playlist moves mp3-->mp3), the audio of the new track starts at the beginning but the Elapsed Time display starts at the "Gap time". So for a 10 second gap, Elapsed Time always starts at 10 seconds.
I checked on MC14, which I've been using for DJing up until recently and this problem does not happen. Gaps are always observed.
[Edit]: Add problem numbers and MC17 info:
MC 17.0.189:
Problem 1 above occurs (Gaped playback not observed when audio format changes).
Problem 2 doesn't occur, Elapsed time always starts at 0 whan focus moves to the next track, but there is a slightly different problem... When play moves from one audio format to another, the audio for the next track starts playing while the elapsed time for the previous track is still counting the Gap time.