A Jumbotron used during the 2009 inauguration. Photo by ajsundby

During last week’s inaugural festivities, some people standing near the Washington Monument missed much of President Obama’s swearing-in speech as a Jumbotron’s audio and video faltered. (See video below.)

But according to the Post, the company that provided the Jumbotrons is still at a loss as to what exactly caused the massive screens to fail at such a key moment:

Tom Sharkoski, CP’s engineering manager for the Mall event and a general manager in its Philadelphia area office, said the screen’s malfunctioning video and audio was not the only problem. Crews in the same area also found themselves unable to communicate on their walkie-talkies during the breakdown, Sharkoski said.

Sharkoski said company officials may never be certain what caused the problem or identify a source of the interference. The company had a dedicated channel for the feed and did not discover any equipment failure, Sharkoski said. “We have not been able to pin it down on what caused the trouble,” he said.

The best that the company has offered by way of explanation is that interference with a microwave signal may have caused the issues. One engineer has some more technical thoughts on what caused the failures—he says it might have been radio interference from protected frequencies used by federal officials.