Other mistake: The first time Rachel brings the team coffee, she has six coffees on a tray. There's five cappuccinos and one regular coffee for Harry. On the tray there is five coffees on one side and one coffee at the other side, obviously being Harry's regular coffee, so that Rachel would be able to tell the them apart. But when she gives Harry a coffee, she gives him one of the five standing together, so he obviously got one of the cappuccinos.
Other mistake: At the end when they are rescuing Harry from the mine, we see a helicopter land and kick up tons of volcanic ash. Given the destructive nature of ash to the engine (as seen in the earlier scene), it would not make any sense to have a helicopter operate anywhere near the area.
Suggested correction: The previous helicopter crashed because of the heavy ash in the air overwhelmed the engine. The later helicopter would presumably be equipped with an appropriate filter to protect the engine. Properly equipped, there's no reason a helicopter wouldn't be used as emergency transport, considering the likely state of the roads. While ash on the ground might moderately increase risk, helicopters are used routinely to fight forest fires.
Volcanic ash is extremely abrasive and corrosive containing parts of glass, dust and debris that will not only cause problems to the engine but will also damage the leading edge of the rotors, altering their aerodynamic abilities.
Other mistake: During the end-credits, someone's title is listed as 'Mr. Bronson's Driver' instead of Brosnan.
Other mistake: When Harry gets out of the truck at the motel to retrieve E.L.F., there appears to be a blue & white storefront sign in the background that is lit, when the rest of the town is dark due to no power. Either that, or it is a really bright, white, non-electric sign that has been completely unaffected by the ash that is coating everything else in town. (01:26:40)
Other mistake: When the lahar slams into the bridge, it seems strange that none of Paul's windows shatter while he's trying to get across. A lot of mud and debris slams into all three vehicles, but their windshields and windows remain intact. Also, the bridge entrance is washed away, but the rest of the bridge remains standing, until it tilts upward and disappears, taking Paul and his van with it.
Suggested correction: Or the white coffee cup was for the guy that's obsessed with her coffee. Considering that it's a little bit bigger than the others and that I'm sure she wrote what each one was on the cups before handing them out, then it's very likely that the one she gave Harry was still a regular. The Grant Heskov-apologies if misspelled-also has the white cup with him, so it is possible that she gave everyone the right one.