Flow Registry with ID <ID> reports that no Flow exists with Bucket <bucketID> , Flow <flowID>

[#1]

Hi, 

Nifi version: 1.20.0

I have created a bucket in NIfi registry, started version control of a workflow on it, and made several version inside it as well. 
What I am trying to achieve now is that I want to import one of the versions from it in another processor group on the same Nifi server.

However, I get below error of bucket and flow not found:

even though I can see the Bucket and different versions inside it on Nifi Registry.

Note: my log file is showing me this error: ERROR [NiFi Registry Web Server-93] o.a.n.r.web.mapper.ThrowableMapper An unexpected error has occurred: java.lang.NullPointerException. Returning Internal Server Error response.

Has anybody experience this same error? Looking fwd to any feedback.

Thanks. 

[#2]

Still awaiting response. Thanks.