Hello Thomas!
I'm running on HANA SPS8 Rev 83.
I've checked user-exits by debug: the first user-exit firing correctly and generates ID (for example '54D1DBB0CE2060E5E10000007F000002'), but the second user-exit doesn't firing.
If I comment the part of request with Busa and $link then the service called without errors and creates record in ZLIB_IND_BASE with generated ID.