Source engine error @ chapter 11

Hi there,

today i was playing BMS @ chapter 11 and when you go into the room where the three academic keep out because they are scared than the door closes and you get shot by a lot of opponents the games laggs extremely at me.

at the first time i died because of the lag and than i get a source engine error:
https://imageshack.us/a/img507/7660/errorchaptereleven.jpg

and short after this when you swim through the dam my hl2.exe crashed when i came up the water. the second time i slowed down and it worked but when you use the speed from the dam the game always crashes

best regards and nice game

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.