The closures, which included Flemingate in Beverley and Meadowhall, Sheffield, took place this week as part of a strategy to close 17 of its 80 locations, affecting 250 jobs.
GBK underwent a company voluntary arrangement (CVA) to gain approval from creditors for the move with a vote on November 9, meaning the 28-day challenge period has not yet finished.
Creditors can challenge a CVA if they believe there to have been unfair prejudice or material irregularity in the process.
The CVA was announced in October after a sustained period of under-performance at the chain.
South Africa’s Famous Brands, which acquired GBK in 2016 for £120m, has previously unveiled stinging losses at the chain.
The firm said in October that it would take a pre-tax impairment charge of 874 million rand (£47.2m) due to the brand’s troubles.
Store closures at GBK represent the latest in a long line of casual dining firms to shut restaurants this year, leaving gaps in high streets and shopping centres.
Gaucho, Carluccio’s, Prezzo, Byron and Jamie’s Italian have all fallen on hard times as costs have rocketed off the back of the Brexit-hit pound, while consumer confidence has nosedived as the economy falters.
The other GBK closures this week included branches in Bedford, Frith Street in Soho (London), Leicester, Metrocentre in Gateshead, Fulham in London, Birmingham Mailbox, Swindon and Stoke.