When science lady is presented with Uno's equations, she isn't told whose they are. After a moment she speaks about Uno's equations.
Early in the movie, when Tomi calls in an accident over the radio, she reports it to have occurred at the intersection of Nelinsgatan and Trozelligatan. These streets run parallel, and never intersect, nor do any tram tracks cross or run along Nelinsgatan. The location is in fact the intersection of Holmstagatan and Trozelligatan.
A scrap magnet cannot lift the body of a Piper Cherokee PA 28 since it is made of (non-magnetic) aluminum.
A Danish aircraft registration have the country code OY, not DK, followed by 3 letters, not 4 numbers.
In an aerial view of Ljuragatan, tram tracks are clearly visible. These tracks weren't there in 1996. That tram line ended at Klingsberg until 2006, when the line end was moved to Ljura. In 2011 the line was extended to Kvarnberget, and the tracks visible in the aerial view are part of that extension.
When Gunnar calls the emergency number from the phone at the UFO Sweden headquarters the number he pushes is 112 the current one for today but was changed the same year as the movie was supposedly recorded in June 1996, dependent on the date in the movie this could be incorrect and if it was recorded prior to June the number should have been 90000.