Led Zeppelin were an English rock band formed in London in 1968. The group consisted of guitarist Jimmy Page, singer Robert Plant, bassist and keyboardist John Paul Jones, and drummer John Bonham. The band's heavy, guitar-driven sound has led them to be cited as one of the progenitors of heavy metal. Their style drew from a wide variety of influences, including blues, psychedelia, and folk music.

Following their triumphant Earls Court appearances, Led Zeppelin took a holiday and planned an autumn tour in America, scheduled to open with two outdoor dates in San Francisco. In August 1975, however, Plant and his wife Maureen were involved in a serious car crash while on holiday in Rhodes, Greece. Plant suffered a broken ankle and Maureen was badly injured; a blood transfusion saved her life. Unable to tour, he headed to the Channel Island of Jersey to spend August and September recuperating, with Bonham and Page in tow. The band then reconvened in Malibu, California. During this forced hiatus much of the material for their next album, Presence, was written.  By this time, Led Zeppelin were the world's number one rock attraction, having outsold most bands of the time, including the Rolling Stones. Presence, released in March 1976, marked a change in the Led Zeppelin sound towards more straightforward, guitar-based jams, departing from the acoustic ballads and intricate arrangements featured on their previous albums. Though it was a platinum seller, Presence received a mixed reaction among fans and the music press, with some critics suggesting that the band's excesses may have caught up with them. Page had begun using heroin during recording sessions for the album, a habit which may have affected the band's later live shows and studio recordings, although this has been denied by Page.  Because of Plant's injuries, Led Zeppelin did not tour in 1976. Instead, the band completed the concert film The Song Remains the Same and the accompanying soundtrack album. The film premiered in New York City on 20 October 1976, but was given a lukewarm reception by critics and fans. The film was particularly unsuccessful in the UK, where, unwilling to tour since 1975 because of their tax exile status, Led Zeppelin faced an uphill battle to recapture the public's affection.  In 1977, Led Zeppelin embarked on another major concert tour of North America. The band set another attendance record, with an audience of 76,229 at their Silverdome concert on 30 April. It was, according to the Guinness Book of Records, the largest attendance to that date for a single act show. Although the tour was financially profitable, it was beset by off-stage problems. On 19 April, over 70 people were arrested as about 1,000 fans tried to gatecrash Cincinnati Riverfront Coliseum for two sold-out concerts, while others tried to gain entry by throwing rocks and bottles through glass doors. On 3 June, a concert at Tampa Stadium was cut short because of a severe thunderstorm, despite tickets indicating "Rain or Shine". A riot broke out, resulting in arrests and injuries.  After the 23 July show at the Day on the Green festival at the Oakland Coliseum in Oakland, California, Bonham and members of Led Zeppelin's support staff were arrested after a member of promoter Bill Graham's staff was badly beaten during the band's performance. The following day's second Oakland concert was the group's final live appearance in the United States. Two days later, as they checked in at a French Quarter hotel for their 30 July performance at the Louisiana Superdome, Plant received news that his five-year-old son, Karac, had died from a stomach virus. The rest of the tour was immediately cancelled, prompting widespread speculation about Led Zeppelin's future.

Answer the following question by taking a quote from the article: What sort of problems occurred off-stage?
On 19 April, over 70 people were arrested as about 1,000 fans tried to gatecrash Cincinnati Riverfront Coliseum