I have a tune that consistently plays at double speed (see here). The 'sudenly broken tune' is probably result of experimental normalization code discussed in several threads here.

Dragi "Bonzi" Raos
Zagreb, Croatia
Q#5196, MkII#80000376, 18GB green
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Dragi "Bonzi" Raos Q#5196 MkII #080000376, 18GB green MkIIa #040103247, 60GB blue