lots of people having this issue. author says it is valve's responsability to fix lol

Yeah I seen that. And I think that is wrong but that's just my opinion
From what I have tested it only happens with the stunstick is in your inventory.
What I mean by that is if you start a new game at the chapter Water Hazard it works just fine because it doesn't give you the stunstick like it does the rest of your weapons that you would have got up to that point

If the game crashes due to you having any other weapons which you're not supposed to have in that area, then it might be a map problem.
So to test this out I recommend adding the RPG, the Crossbow, the Bugbait, and/or the Super Gravity Gun to see if you can reproduce the crash using other weapons.
And if you can reproduce this crash using other weapons, then it is absolutely a map problem. :3

引用自 Fluffy Failure：

If the game crashes due to you having any other weapons which you're not supposed to have in that area, then it might be a map problem.
So to test this out I recommend adding the RPG, the Crossbow, the Bugbait, and/or the Super Gravity Gun to see if you can reproduce the crash using other weapons.
And if you can reproduce this crash using other weapons, then it is absolutely a map problem. :3

100% a map issue

引用自 thereallintman：

Yeah I seen that. And I think that is wrong but that's just my opinion
From what I have tested it only happens with the stunstick is in your inventory.
What I mean by that is if you start a new game at the chapter Water Hazard it works just fine because it doesn't give you the stunstick like it does the rest of your weapons that you would have got up to that point

M8, you understand that you're NEVER meant to HAVE the Stunstick at all so yes this is a matter that Valve can only fix and they're likely not going to simply because they designed the game so you only have the Crowbar. Now if someone was able to somehow bring whatever code is used in Garry's Mod that permits you to not only have the Stunstick and never experience the crash problem during Water Hazard then MAYBE it can be fixed without Valve's involvement, but that's a giant maybe because LUA code isn't the same as whatever the code in HL2 is.