diff --git a/iframe.html b/iframe.html
index 81fa320..bd2d3e1 100644
--- a/iframe.html
+++ b/iframe.html
@@ -1948,13 +1948,19 @@
                             return;
                         }
                         
-                        // Check if this is the only unlocked source (will be forced to fixed percentage)
+                        // Check if this source has no flexibility (either only unlocked or no percentage available)
                         const otherUnlockedSources = this.foodSources.filter((fs, index) => 
                             fs.id !== id && !fs.isLocked
                         );
                         
-                        if (otherUnlockedSources.length === 0) {
-                            // This is the only unlocked source - don't update display, just call adjustPercentages
+                        // Calculate available percentage for this source
+                        const lockedSources = this.foodSources.filter(fs => fs.id !== id && fs.isLocked);
+                        const totalLockedPercentage = lockedSources.reduce((sum, fs) => sum + fs.percentage, 0);
+                        const otherUnlockedPercentage = otherUnlockedSources.reduce((sum, fs) => sum + fs.percentage, 0);
+                        const availablePercentage = 100 - totalLockedPercentage - otherUnlockedPercentage;
+                        
+                        if (otherUnlockedSources.length === 0 || availablePercentage <= 0) {
+                            // This source has no flexibility - don't update display, just call adjustPercentages
                             // which will force it to the correct value and update display properly
                             this.adjustPercentages(id, parseInt(percentageSlider.value));
                             return;