I can recall maybe 5 anxious episodes involving other gliders but here is my solo self inflicted close call.
Flying an old Skylark 3 glider, wind was 25 kts straight down the strip, thermic enough to make the aerotow interesting, the lift was too broken to gain height so joined the circuit, on the down wind leg I allowed the speed to drop then turned base leg.
The glider stalled with wing drop in the gradient, just managed to level the wings in time to flop over the threshold, right in front of the CFI. His comments, " never do that again, go and have a coffee, then come back and show me how it should be done".
I got away with that one!!, but learned from it.