In recent release of primeng, if we set baseZIndex for a autocomplete in a page. It impacts z-index of all autocomplete fields in that page. Earlier baseZIndex value for each autocomplete was mutually exclusive.
To check, you can open primeng autocomplete demo page on stackblitz. Add baseZIndex for any one of the autcomplete. Now inspect autocomplete search dropdown for all autocomplete fields. The z-index value of all of them is impacted.