My guess is that its a software issue:
Most digital volume controls control volume in 2 ways: either by setting a specific volume setting for each "click" of the volume knob, or more common, each "click" reduces or increases volume by a certain factor, relative to the volume value when the knob is turned.
So, if you're cruising along with the volume turned up to 11, and you turn it down 10 clicks down to 0, each click took about 10% off the volume amount, BUT, when you start from 0 (or 0.000001), 10% of that for an increase really isn't much, so you need to give a whole bunch more clicks to get back up to the audible range.
One way you can increase this is to give a turn of the knob (multiple clicks), wait a moment, then do another turn, wait, then another. Each set of clicks adds its factored amount from the starting value, each pause will give the software a new starting value.
Or you can just use the Mute Button...