A further tour of the US was planned for December 1976, but it had to be cancelled when, on 23 November, Brian Robertson suffered a hand injury when trying to protect fellow Glaswegian, singer and friend Frankie Miller in a fracas at the Speakeasy Club in London. Miller had been jamming onstage with the reggae band Gonzalez, but had been drunk, offending Gonzalez guitarist Gordon Hunte. Hunte attacked Miller with a bottle in the dressing room, and Robertson intervened, suffering artery and nerve damage to his hand.Robertson subsequently broke Hunte's leg, broke the collarbone of another man, and headbutted another, before being hit on the head with a bottle, rendering him unconscious.
Robertson maintains that, contrary to reports at the time, he was not drunk and had only gone to the venue for a meal. Lynott was angry and replaced Robertson with Gary Moore for another tour of the States in January–March 1977, this time supporting Queen. The tour was a success and Lynott asked Moore to stay on, but he returned to his previous band, Colosseum II. Robertson had not been sacked but was unsure of his position and made plans to start another band with Jimmy Bain of Rainbow. Before the American tour, Lynott had also invited Irish guitarist Jimi Slevin to "try out a few things" with Thin Lizzy, prompting speculation that the ex-Skid Row member could replace Robertson.
Thin Lizzy flew to Canada in May 1977 as a trio to record Bad Reputation, with Gorham handling all the guitar parts. A month into the sessions, at Gorham's urging, Robertson joined them, in his own words, "as a session player" and in Lynott's words, "as a guest". Robertson added lead guitar tracks to three songs as well as rhythm guitar and keyboards, and was officially reinstated in July. The album was released in September and sold well, reaching no. 4 in the UK, after a successful single, "Dancing in the Moonlight (It's Caught Me in Its Spotlight)". Also in 1977, Thin Lizzy headlined the Reading Festival.