Question: Why didn't Ethan just give Nyah one of his guns after she infected herself? She could have easily killed Ambrose and others with a surprise attack since they were more interested in keeping her alive and she wanted Ethan to kill her anyway. She had better odds of surviving that way than the impossible plot that followed. She could have killed everyone but Ambrose and he may have let it happen in order to still have a chance at selling the virus.
Question: Throughout the film, Hugh Stamp's accent keeps changing, where exactly is he supposed to be from?
Question: What is supposed to be in those biohazard tanks that makes them explode so violently when shot. Considering what is stored inside them that seems like a stupid way of storing dangerous things.
Continuity mistake: The tyres on the crotch rocket motorcycles they were riding kept changing from knobbly tyres to road slicks, back and forth depending on what terrain they were on. Easiest to see when Ethan skids on the road to avoid the white van - clear shot of slick tyres - then about 30 seconds later they're on the dirt, he skids into the old car and you can easily see that he's got off-road tyres front and back.