I have a block in my game that summons  boss when its activated by right click. Since the boss 2 hit kills a player with no armor, I decided to also make it be activated by redstone.

 

The redstone wires connect to the block, but sometimes the block doesn't get activated:

 

Here's the block class:

package tlhpoe.fs.block;

import net.minecraft.block.Block;
import net.minecraft.block.material.Material;
import net.minecraft.client.renderer.texture.IIconRegister;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.init.Blocks;
import net.minecraft.util.IIcon;
import net.minecraft.util.MathHelper;
import net.minecraft.world.IBlockAccess;
import net.minecraft.world.World;
import tlhpoe.fs.entity.boss.EntityMonkeysaur;
import cpw.mods.fml.relauncher.Side;
import cpw.mods.fml.relauncher.SideOnly;

public class BlockMonkeysaurAltar extends Block {
public IIcon iSide, iTop;

public BlockMonkeysaurAltar() {
	super(Material.rock);
}

@Override
@SideOnly(Side.CLIENT)
public IIcon getIcon(int side, int p_149691_2_) {
	if(side == 1)
		return iTop;
	return iSide;
}

@Override
@SideOnly(Side.CLIENT)
public void registerBlockIcons(IIconRegister p_149651_1_) {
	this.iSide = Blocks.gold_block.getBlockTextureFromSide(0);
	this.iTop = p_149651_1_.registerIcon("fs:monkeysaurAltar");
	this.blockIcon = this.iTop;
}

@Override
public boolean onBlockActivated(World w, int x, int y, int z, EntityPlayer p_149727_5_, int p_149727_6_, float p_149727_7_, float p_149727_8_, float p_149727_9_) {
	if(!w.isRemote) {
		w.setBlock(x, y, z, Blocks.air);
		EntityMonkeysaur e = new EntityMonkeysaur(w);
		e.setLocationAndAngles(x, y, z, MathHelper.wrapAngleTo180_float(w.rand.nextFloat() * 360.0F), 0.0F);
		e.rotationYawHead = e.rotationYaw;
		e.renderYawOffset = e.rotationYaw;
		w.spawnEntityInWorld(e);
		e.playLivingSound();
	}
	return true;
}

@Override
public void onNeighborBlockChange(World w, int x, int y, int z, Block b) {
	if(w.isBlockIndirectlyGettingPowered(x, y, z)) {
		onBlockActivated(w, x, y, z, null, 0, 0, 0, 0);
	}
}

@Override
public boolean canConnectRedstone(IBlockAccess world, int x, int y, int z, int side) {
	if(side != -1)
		return true;
	return false;
}
}

Descriptive comment for isBlockIndirectlyGettingPowered() is:

 

'Used to see if one of the blocks next to you or your block is getting power from a neighboring block. Used by items like TNT or Doors so they don't have redstone going straight into them. Args: x, y, z.'

 

Your block is probably getting indirectly powered by the ones underneath them. You could try checking in the repeater class for how it detects its direct power.