diff --git a/src/battle-scene.ts b/src/battle-scene.ts
index e659b588208..061fc6e28f2 100644
--- a/src/battle-scene.ts
+++ b/src/battle-scene.ts
@@ -1233,6 +1233,11 @@ export default class BattleScene extends SceneBase {
       newDouble = !!double;
     }
 
+    // Disable double battles on Endless/Endless Spliced Wave 50x boss battles (Introduced 1.2.0)
+    if (this.gameMode.isEndlessBoss(newWaveIndex)) {
+      newDouble = false;
+    }
+
     if (!isNullOrUndefined(Overrides.BATTLE_TYPE_OVERRIDE)) {
       let doubleOverrideForWave: "single" | "double" | null = null;
 
diff --git a/src/game-mode.ts b/src/game-mode.ts
index 8f1bb9356e6..0f997bf651e 100644
--- a/src/game-mode.ts
+++ b/src/game-mode.ts
@@ -236,7 +236,7 @@ export class GameMode implements GameModeConfig {
      * @returns true if waveIndex is a multiple of 50 in Endless
      */
   isEndlessBoss(waveIndex: integer): boolean {
-    return !!(waveIndex % 50) &&
+    return waveIndex % 50 === 0 &&
         (this.modeId === GameModes.ENDLESS || this.modeId === GameModes.SPLICED_ENDLESS);
   }
 
diff --git a/src/modifier/modifier.ts b/src/modifier/modifier.ts
index 7aa4b9308d1..ac8dc556b98 100644
--- a/src/modifier/modifier.ts
+++ b/src/modifier/modifier.ts
@@ -3631,7 +3631,7 @@ export class EnemyEndureChanceModifier extends EnemyPersistentModifier {
     super(type, stackCount || 10);
 
     //Hardcode temporarily
-    this.chance = .02;
+    this.chance = 2;
   }
 
   match(modifier: Modifier) {
@@ -3639,11 +3639,11 @@ export class EnemyEndureChanceModifier extends EnemyPersistentModifier {
   }
 
   clone() {
-    return new EnemyEndureChanceModifier(this.type, this.chance * 100, this.stackCount);
+    return new EnemyEndureChanceModifier(this.type, this.chance, this.stackCount);
   }
 
   getArgs(): any[] {
-    return [ this.chance * 100 ];
+    return [ this.chance ];
   }
 
   /**
@@ -3652,7 +3652,7 @@ export class EnemyEndureChanceModifier extends EnemyPersistentModifier {
    * @returns `true` if {@linkcode Pokemon} endured
    */
   override apply(target: Pokemon): boolean {
-    if (target.battleData.endured || Phaser.Math.RND.realInRange(0, 1) >= (this.chance * this.getStackCount())) {
+    if (target.battleData.endured || target.randSeedInt(100) >= (this.chance * this.getStackCount())) {
       return false;
     }