I updated NXSDK to recent series 6.4.x and boom no love from WWise.
Thankfully the integration demo experiences same behavior as my app:
Assertion Failed! D:/Jenkins/ws/wwise_v2018.1/Wwise/SDK/source/SoundEngine/3rdParty/Common/tlsf/tlsf.cpp:555: block_size(block) >= size
Assertion Failed! D:/Jenkins/ws/wwise_v2018.1/Wwise/SDK/source/SoundEngine/3rdParty/Common/tlsf/tlsf.cpp:501: block_is_free(block) && "block must be free"
Assertion Failed! D:/Jenkins/ws/wwise_v2018.1/Wwise/SDK/source/SoundEngine/3rdParty/Common/tlsf/tlsf.cpp:230: !block_is_last(block)
So... is this already known, workaround available, fix underway, or what?