ORA-600 on table scans after create pluggable local undo

Using create pluggable to create a hot copy of production database in the development environment

Windows 2016

Oracle 12.2.0.1

Database size > 600GB

story:

drop pluggable database copyDB

create pluggable database copyDB from prodDB@production;

database created  (in 29 minutes.)

alter pluggable copDB open;

For each application_table loop

     select count(*) from <table_name>

end loop;

~~20% of tables scanned report ora-600, relating to missing undo segments.

VerifyDatabase reports no errors.

SR opened with Oracle since October 2018.  Oracle identified missing undo segments causing the problem, but cannot reproduce the problem internally.

I cannot NOT reproduce the error, ie. it happens on every copy.

My workaround is to drop and create the copyDB's local undo tablespace.  Achieved by toggling CDB from local, to shared, to local undo.