The pointer files (PTR1/2) are not initialized when .CHART INITIALIZE is called, so each time you call .CHART RENDER, the previously defined pointers appear as well as the one(s) you intended for the current chart.
The PRT1/2 files are not linked to a particular CHTSPEC record, so if you are working with multiple charts of this type, the pointer will appear on all charts, not just the current one (when rendered)
Overview
Release 5.1.0 of the APPX Utility includes a new designer API which can be used to create charts within an APPX application. This API provides APPX Designers with a robust set of subroutines which can be called to design charts, define datasets, and render charts using datasets. These charts can then be dynamically embedded in APPX menus, input screens, and PDF reports.