Steph,
As far what I see is, 5.3.12.0 is part of your 5.3.12.1. meaning if you install 12.1 it will 1st install 12.0 and update it to 12.1.
Now do this, on the NIM server run
# nim -o showres <resource_name> | grep bos.mp.5.3.12.1
where resource_name=your lpp_source
If the file set exist you will see it, now do this
# installp -qld bos.mp.5.3.12.1 (the output will be similar to below example, see it has 'I' {under 'I/U Q Content'} which is installable and not upgrade file set. If it has 'I', and I am sure it will then you should be good).
I took the example of lsof file set.
Fileset Name Level I/U Q Content
====================================================================
lsof.base 6.1.0.4820 I N usr,root
# List Of Open Files
Also try to run in the directory of your binaries
# inutoc .
SARFARAZ AHMED SYED,
Sr. Systems Engineer