MIDI error compiling source

[Knute Snortum]

The attached LilyPond file producing "programming errors" below.  I've pared down the source so that it's smaller but still emits a warning.  Anyone know why the warnings are produced?  The PDF and MIDI files seem fine.  It's just that I don't like producing error messages.

Starting lilypond-windows.exe 2.18.2 [midi_error_test.ly]...

Processing `.../midi_error_test.ly'

Parsing...

Interpreting music...

Preprocessing graphical objects...

Interpreting music...

MIDI output to `midi_error_test.mid'...

programming error: Going back in MIDI time.

continuing, cross fingers

programming error: Going back in MIDI time.

continuing, cross fingers

programming error: Going back in MIDI time.

continuing, cross fingers

Finding the ideal number of pages...

Fitting music on 1 page...

Drawing systems...

Layout output to `midi_error_test.ps'...

Converting to `./midi_error_test.pdf'...

Success: compilation successfully completed

Completed successfully in 2.7".

Knute Snortum

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midi_error_test.ly
Description: Text Data