After bird-killing glass and outer cladding falling off, now further problems with the external envelope were reported, as well as escalator malfunction around the stadium.

U.S. Bank Stadium may be one of the most iconic NFL venues, but it's also increasingly controversial. Despite the massive budget of over $1.1 billion there are issues arising quite often, every several weeks.

First it was the birds. In late February local chapter of Audubon released its report which gave low yet disturbing number of birds killed after having hit the large glass-clad facades.

During the 2016 fall migration period a total of 60 birds were observed dead, over 50% of them found under the largest western facade. This confirms prior warnings from Audubon that too much of the almost transparent glass could prove deadly for migrating birds.

© Meet Minneapolis

Almost at the same time U.S. Bank Stadium's snow gutter system proved flawed and required repairs worth some $3-4 million (covered by the contractor). Then in March a small number of the stadium's zinc cladding came loose after high winds. It wasn't the first accident of this kind, which prompted fears that more serious upgrades could be needed.

During last week's meeting of the Minnesota Sports Facilities Authority it surfaced that while the zinc panelling is now fixed safely in place, there may be issues beneath the surface. The MSFA is taking a closer look at the durability of the fastener system and the durability of the water resistant barrier on the outside of the stud wall behind the panels.

At this point, the MSFA does not know exactly what needs to be done to the building envelope or how much it may cost. The authority is in talks with general contractor M.A. Mortenson Co. And subcontractor for the panelling, MG MgGrath,

“We’re still investigating the extent of the issues — whether it is a problem, what it will cost and who will pay. All that is still in discussion,” MSFA CEO Rick Evans said during the post-meeting interview. “We just want to make sure [the envelope] is as designed and what we paid for.”