When using ADDRESS TSO/OSF/OSFTSL/OSFTSP and passing arguments to the REXX program that contain the string "SYS" or "SY" this string is being considered as the keyword SYSTEM introduced by the PTF LU11931 and causing errors like the below:
OPS4327E Current system ID (SSSS) is not defined to MSF
OPS/MVS 14.0 with LU11931 applied
PTF LU13019 has been published to solve this problem