Slowest Service Ever 30+mins in drive thru (1 car ahead of me)

Burger King East Rand Boksburg (Rietfontein) is by far the slowest Burger King i have ever gone to. I have been to more than 5 Burger king outlets in SA including the western cape and Secunda. The first time i went there(earlier this year) i waited 40mins, in the drive thru, there were 3 cars in front of me... I thought it must be a bad day, Last week Tuesday 26 June 2018,l i was heading to the Airport and thought let me quickly pop in at Burger King, with 1 car ahead of me in the drive thru ( who was already waiting), i waited 30mins for a single burger and a chocolate Sundae, when i finally arrived at the next window, they Sundae was not even prepared yet. I had to rush to make the airport in time. on average i spend about 3-5mins in most other Burger King outlets.