Minecraft – Tekkit Classic blocks wouldn’t drop after being destroyed (single-player)

I've done some number crunching and I think I have your answer for you. These numbers assume that (a) you use the mining method in the accepted answer you link, (b) that the ores are uniformly distributed, and (c) that you're running a version of Minecraft between 1.6.0 and 1.7.3 (the chart you link hasn't been updated for 1.8 yet).

Mining for an hour with ~30 iron picks should yield you:

• 7,201 cobblestone
• 77 coal
• 308 redstone
• 46 iron
• 8 gold
• 8 diamond
• 37 lapis lazuli

Similarly, using ~6 diamond picks should get:

• 9,166 cobblestone
• 98 coal
• 392 redstone
• 59 iron
• 10 gold
• 10 diamond
• 47 lapis lazuli

As you can see, the iron and diamond yields are far below what goes into the picks. In other worlds, through solid stone, you operate at a loss. Caves make an enormous difference when it comes to mining efficiency.

(All this, of course, assumes my math is correct. Feel free to double-check my work in the spreadsheet.)

It's just your game lagging, so if you wait a while you will see that the actions you have attempted to make will happen, but if you for example: break a block and it reappears, then you break a different block, only the first block will be broken. The only recommendation I have to fix this lag spike is to get rid of big mods, and get rid of mods you don't want. Doing either of these reduces the strain you're putting on your computer and reduces the lag.