Actually, the TBS420 is valid, it seems that the JCL cannot access TBS210.PDS.PROCLIB.
that' s a common misunderstandig of ISPF processing
ISPF can store <things> in packed format to save space
when browsin/viewing/editing ISPF will under the covers <unpack> the <thing>
so You will not be aware of the <packed> status
to fix the issue just edit the thing, in the command line enter PACK OFF ( IIRC) and type
sometimes just hitting PF3 does not change the packed status ( could have been some missing fixes )
the DSS.... messages are certainly from the jcl scanner