Error in NBI serviceSpecification ap

if service category is CST or NSST  and it is composed of nested service then service is not getting distributed in NBI.  

 When we try to fetch specifications for CST or NSST (having nested service) , getting error 

https://xxxxxx:30274/nbi/api/v4/serviceSpecification/27bc0242-b785-40df-bfb8-5bffcf2dc5f2

{   "timestamp": 1606468694326,   "status": 500,   "error": "Internal Server Error",   "message": "No message available",   "path": "/nbi/api/v4/serviceSpecification/27bc0242-b785-40df-bfb8-5bffcf2dc5f2" }