5th Small Stone: Time marches on

The clock on the living room wall passes time erratically.  It does not pick up the tick tock beat one would expect. I try to find the pattern in it's metronome like song.  pth pth pock pth pock tick tock click.  The cadence is clear but every tone just slightly different than the one before.  It's generally showing the correct time.  Sometimes a few minutes late, sometimes a few minutes early. Should I buy a new clock?