When Rockwell Automation released Version 16 (and later) revisions of RSLogix5000 programming software for ControlLogix systems, they had to change the starting point of the timebase for the processor's internal clock and added some new features as a result of the change. Please see the Rockwell Automation KB article 37953 - New ControlLogix Time Settings with v16 and up.
Any ProSoft MVI56 module that supports internal clock functions, especially the MVI56-AFC, MVI56-DNP and any MVI56 modules that support IEC protocols, like 101S, 101M, 103M, 104S, etc. can be affected by this change.
ProSoft has created new versions of sample ladder logic and new Add-On Instructions (AOI; but only for selected modules) that have corrected any incorrect references to WALLCLOCK and other clock-related ControlLogix functions.
If you have converted older ladder to Version 16 (or later) and are experiencing clock inaccuracy problems, please download and implement the latest sample ladder or AOI from the ProSoft product web page for your specific module or contact ProSoft Technical Support for assistance.