10 sec delay on play wave file in IVR

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We notice that in versione 9 using abyss server we have a 10 second delay when 3CX play wave audio files associated to an IVR. File are 44.1 Khz 16 bit mono.
We have no problem with version 8 but after upgrade we notice this issue.
OS is Windows 2008 Server R2 with Desktop Experience enabled.
Any solution ?

 

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This problem is not always present but randomly in about 20% of calls to an IVR. But if we dial 999 for voicemail delay is always about 10 seconds. Unfortunately not in the first call only.