Safety calculation for a deep excavation (80 ft+ deep)

Hi everyone,

after running the "safety" calculation for the default number of steps (100), it didn't stabilize the Msf, so I extended it to 400 steps. It stabilized the FoS to around 2.6 for about 100 steps, while the lateral displacement I was monitoring continued to grow. At some point it hit a critical displacement value and the FoS dropped to 0 very rapidly (see below). I am having a hard time interpreting this. Does every simulation of a deep excavation eventually reach a FoS of 0 if the number of steps are increased enough or is this just the case for this project? Below are screenshots for reference.