Fix white textures on vanilla models sharing a TXD slot

Author: Dutchman101

Client/game_sa/CRenderWareSA.TextureReplacing.cpp

@@ -5468,13 +5468,38 @@ bool CRenderWareSA::ModelInfoTXDAddTextures(SReplacementTextures* pReplacementTe
             }
             else if (itPrevIsolated == g_IsolatedTxdByModel.end())
             {
-                // Keep vanilla replacements on a private TXD so later model
-                // loads and child TXDs dont pick them up from the shared slot.
-                if (!AllocateIsolatedTxdForVanillaModel(usModelId, usCurrentTxdId))
+                // Only isolate when the shared TXD already has replacement
+                // textures for a different model - multiple CClientTXDs
+                // imported to different models on the same slot would corrupt
+                // each other. Without a conflict, let textures go into the
+                // shared TXD so other models on the same slot can still find
+                // them through SA's texture walk.
+                bool bHasConflict = false;
+                auto itExisting = ms_ModelTexturesInfoMap.find(usCurrentTxdId);
+                if (itExisting != ms_ModelTexturesInfoMap.end())
+                {
+                    for (const SReplacementTextures* pExisting : itExisting->second.usedByReplacements)
+                    {
+                        if (!pExisting || pExisting == pReplacementTextures)
+                            continue;
+
+                        if (pExisting->usedInTxdIds.count(usCurrentTxdId) > 0 &&
+                            pExisting->usedInModelIds.count(usModelId) == 0)
+                        {
+                            bHasConflict = true;
+                            break;
+                        }
+                    }
+                }
+
+                if (bHasConflict)
                 {
-                    AddReportLog(9401, SString("AllocateIsolatedTxdForVanillaModel failed for model %u, deferring", usModelId));
-                    QueuePendingReplacement(usModelId, pReplacementTextures, 0, 0);
-                    return false;
+                    if (!AllocateIsolatedTxdForVanillaModel(usModelId, usCurrentTxdId))
+                    {
+                        AddReportLog(9401, SString("AllocateIsolatedTxdForVanillaModel failed for model %u (conflict), deferring", usModelId));
+                        QueuePendingReplacement(usModelId, pReplacementTextures, 0, 0);
+                        return false;
+                    }
                 }
             }
             else
@@ -5603,8 +5628,9 @@ bool CRenderWareSA::ModelInfoTXDAddTextures(SReplacementTextures* pReplacementTe
             }
             else
             {
-                QueuePendingReplacement(usModelId, pReplacementTextures, 0, 0);
-                return false;
+                // Non-isolated vanilla model during reapply: fall through to
+                // the shared TXD injection below so textures get re-added
+                // after a streaming reload.
             }
         }
     }