I'm sure this isn't just me. When the blocks reach the top of the screen and the ticking starts, the game becomes very sluggish and it's difficult to grab a block from the column and move it out. It's as if you're hogging up the CPU for some reason.
The ticking noise sounds disjointed as well. As tho you're using a longer sound than the interval between them. Maybe think about creating a new sound for this which is suited.
I also recommend making it last fractionally longer.
I've got the same experience here. I frantically swipe at the top block hoping I can grab it and move it out in time, which sometimes works. Also, I've noticed sometimes it's game over, and sometimes it's "this is your first time - we'll clear some blocks for you" with no reason I can come up with. And it's clearly not my first time if I'm playing on speed 46.
Additionally, I'd recommend some kind of game-over effect: the board blowing up or, alternatively, the board getting filled in by rocks to look like a cave-in or something. Just jumping to the "finished mining" screen doesn't look like anything really went wrong. Also, I'd recommend a hit in the character's XP for failing too.
As a complete side-note, the ticking sound being the same as the smith clock gave me a weird idea. In the mine, you die/fail if the blocks are at the top of the screen for too long, right? What if in the smith, it just made the clock run really quickly while the blocks are at the top. Like at the speed of the ticking (3x or so). So you don't exactly fail for filling the screen, but it makes your job that much harder. Just a thought.