Only some of the Identifiers in PATSTAT data are "stable", meaning they identify the same records across editions of PATSTAT. For details please see the Data Catalog or PATSTAT Global, section 4.3.2.
While PERSON_ID is such as stable identifier, PSN_NAME (the PATSTAT Standardised Name) is not. So, as you observed, the same value of PSN_NAME will identify different records of the person table in different PATSTAT editions.
Conceptually it is not possible to have both PERSON_ID and PSN_NAME stable within the same records, if the assignment of a harmonized name to a person is not absolutely fix - which it is not, due to improvements in the harmonisation algorithm and data corrections.
So to compare data across versions, you must also keep stable identifiers like PERSON_ID, APPLN_ID, PAT_PUBLN_ID etc. If you have not done so, then you could re-match person records of different versions via
name (and address). If this is not possible, please contact the PATSTAT helpdesk at email@example.com
for a remedy.
As a side note: Till autumn 2015 the now-called attribute PSN_NAME was called HRM_L2_ID. For better comprehensibility, we did a simple rename.
So in short: the PSN_ID is not stable accross releases, but data can be matched via the PERSON_ID.