Program: 135104
Project: 135104
Buggy source:
@Override public void onWailaBlockDescription(ItemStack stack,List<String> tooltip,IWailaDataAccessor access,IWailaConfigHandler config){
  MovingObjectPosition pos=access.getPosition();
  Block block=access.getBlock();
  ItemStack item=access.getPlayer().getHeldItem();
  String tool=(block != null) ? block.getHarvestTool(access.getMetadata()) : "String_Node_Str";
  int blockLevel=block.getHarvestLevel(access.getMetadata());
  int itemLevel=(item != null) ? item.getItem().getHarvestLevel(item,tool) : 0;
  if (tool != null && tool.equalsIgnoreCase("String_Node_Str")) {
    if (block == Blocks.stone)     tool="String_Node_Str";
    if (block == Blocks.planks)     tool="String_Node_Str";
  }
  if (item != null && (item.getItem().getToolClasses(item).contains(tool) || ModuleTinkers.canHarvest(item,tool))) {
    if (config.getConfig(showHarvestable) && (blockLevel <= itemLevel || blockLevel == 0))     tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + ((EnumChatFormatting.DARK_GREEN + StatCollector.translateToLocal("String_Node_Str"))));
 else {
      tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + EnumChatFormatting.RED+ StatCollector.translateToLocal("String_Node_Str"));
      if (config.getConfig(showTier))       tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + blockLevel);
    }
    return;
  }
  if (tool != null && config.getConfig(showTool))   tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + tool);
}

Fixed version (ground truth):
@Override public void onWailaBlockDescription(ItemStack stack,List<String> tooltip,IWailaDataAccessor access,IWailaConfigHandler config){
  MovingObjectPosition pos=access.getPosition();
  Block block=access.getBlock();
  ItemStack item=access.getPlayer().getHeldItem();
  String tool=(block != null) ? block.getHarvestTool(access.getMetadata()) : "String_Node_Str";
  int blockLevel=block.getHarvestLevel(access.getMetadata());
  int itemLevel=(item != null) ? item.getItem().getHarvestLevel(item,tool) : 0;
  if (tool != null && tool.equalsIgnoreCase("String_Node_Str")) {
    if (block == Blocks.stone)     tool="String_Node_Str";
    if (block == Blocks.planks)     tool="String_Node_Str";
  }
  if (item != null && (item.getItem().getToolClasses(item).contains(tool) || ModuleTinkers.canHarvest(item,tool))) {
    if (config.getConfig(showHarvestable) && (blockLevel <= itemLevel || blockLevel == 0))     tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + ((EnumChatFormatting.DARK_GREEN + StatCollector.translateToLocal("String_Node_Str"))));
 else {
      tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + EnumChatFormatting.RED+ StatCollector.translateToLocal("String_Node_Str"));
      if (config.getConfig(showTier))       tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + blockLevel);
    }
    return;
  }
  if (tool != null && config.getConfig(showTool))   tooltip.add(StatCollector.translateToLocal("String_Node_Str") + "String_Node_Str" + Utilities.upperCase(tool));
}