The mercs tell J.D. that they need the dynamite because there is "ten feet of solid concrete" in their way, yet when they detonate the bundle of dynamite, the wall surrounding the blasted-out hole is only an inch or two thick.
The mercs state that there is "ten feet of solid concrete" in their way, yet they would have no way of knowing just from looking at the surface how thick it is.
The merc tells his partner that he has "enough dynamite to blast clear to China", yet when they attach a large bundle of the dynamite-sticks to the wall, they use a short fuse and merely move away a few yards; when the charge goes off, only a small feeble boom is heard ("In Hazzard, there are so many vehicles backfiring that nobody would take any notice of that bang"), and no smoke even comes out of the open manhole.
When Vance tries to reach Daisy on the CB after they get back to the farm, he says "Bo Peep to Lost Sheep". It should be the other way around.