It is not recommended to use the API CyU3PDebugPrint() inside a callback function. This is because it will delay the processing of DMA interrupts on all channels in the system. This is documented in page 46 of the document Getting started with FX3 SDK which can be found in the following location:
C:\Program Files (x86)\Cypress\EZ-USB FX3 SDK\1.3\doc\firmware
Note: This path may change depending on the installation directory of FX3 SDK.