--- a/src/MacSrc/Modding.c	2026-07-19 13:11:51.000000000 +0200
+++ b/src/MacSrc/Modding.c	2026-09-27 19:44:24.718059783 +0200
@@ -27,6 +27,11 @@
 char *modding_additional_files[MAX_MOD_FILES];
 int num_mod_files;
 
+// One filenum per modding_additional_files[] entry, or -1 if not open yet -
+// lets LoadModFiles() close a mod file's previous handle before reopening it
+// (see LoadModFiles() below for why it needs to be called more than once).
+static int32_t modding_loaded_filenum[MAX_MOD_FILES];
+
 int StringEndsWith(char *src, char *dst) {
     char *s = strrchr(src, '.');
 
@@ -86,6 +91,7 @@
     modding_archive_override = NULL;
     for (int i = 0; i < MAX_MOD_FILES; i++) {
         modding_additional_files[i] = NULL;
+        modding_loaded_filenum[i] = -1;
     }
 
     // Now go process args
@@ -135,10 +141,24 @@
 }
 
 int LoadModFiles() {
+    // Called again by obj_set_secondary_properties() (objsim.c) after it
+    // re-opens the base game's own object art files, which would otherwise
+    // silently reclaim any resource ID a mod file already overrode here (see
+    // ResReadDirEntries() in resfile.c - opening a file re-registers every
+    // resource ID it contains, last one in wins, with no check for whether
+    // an ID is already claimed). Re-registering means actually re-opening
+    // (there is no "just re-register" primitive), so a mod file already open
+    // from an earlier call is closed first - one open handle per mod file at
+    // a time, rather than leaking a fresh resFile[] slot on every repeat call
+    // (new game, load game - object_data_load() can run more than once per
+    // process).
     for (int i = 0; i < num_mod_files; i++) {
         if (modding_additional_files[i] != NULL) {
+            if (modding_loaded_filenum[i] >= 0) {
+                ResCloseFile(modding_loaded_filenum[i]);
+            }
             printf("Loading mod file %s\n", modding_additional_files[i]);
-            ResOpenFile(modding_additional_files[i]);
+            modding_loaded_filenum[i] = ResOpenFile(modding_additional_files[i]);
         }
     }
 
--- a/src/GameSrc/objsim.c	2026-07-19 13:11:51.000000000 +0200
+++ b/src/GameSrc/objsim.c	2026-09-27 19:44:17.014441306 +0200
@@ -43,6 +43,7 @@
 #include "gettmaps.h"
 #include "lvldata.h"
 #include "mapflags.h"
+#include "Modding.h"
 #include "objart2.h"
 #include "objart3.h"
 #include "objects.h"
@@ -1877,6 +1878,13 @@
         //              Warning(("Problem opening object art cache!\n"));
         return (ERR_NOEFFECT);
     }
+    // The two opens above re-register every resource ID objart2.res/
+    // objart3.res contain, reclaiming any of them a mod file already
+    // overrode (see LoadModFiles() in Modding.c) - restore mod priority
+    // for the reftable reads below. load_dynamic_memory() (cybmem.c) reopens
+    // these same two files again later, persistently, for actual rendering -
+    // restoring priority there too.
+    LoadModFiles();
 
     // Now go and set specific computed data, like frame counts
     for (i = 0; i < NUM_CRITTER; i++) {
--- a/src/GameSrc/cybmem.c	2026-07-19 13:11:51.000000000 +0200
+++ b/src/GameSrc/cybmem.c	2026-09-27 19:44:24.718059783 +0200
@@ -33,6 +33,7 @@
 #include "textmaps.h"
 #include "objcrit.h"
 #include "dynmem.h"
+#include "Modding.h"
 #include "Shock.h"
 #include "sideicon.h"
 #include "criterr.h"
@@ -120,6 +121,15 @@
                 critical_error(CRITERR_RES | 8);
         }
 
+        // The four opens above re-register every resource ID their files
+        // contain, reclaiming any of them a mod file already overrode (see
+        // LoadModFiles() in Modding.c) - these are the persistent handles
+        // actual gameplay renders from (unlike obj_set_secondary_properties()'s
+        // own transient open/close of objart2.res/objart3.res for reading
+        // frame-count metadata), so this is the last point mod priority needs
+        // restoring before rendering.
+        LoadModFiles();
+
         loadcount |= mask;
     }