Update: Radeon RX series appears to function without the need for -vulkan launch parameter. If you are using an Nvidia GPU and are willing to test the mod without vulkan, then leave a comment on the main page listing your GPU characteristics and information whether you encountered Engine Error crashes before Water Hazard.

Note: +r_hunkalloclightmaps 0 is still required in all conditions.

While vulkan is essential for the maps beyond the Kleiner's lab, it might introduce stuttering even in vanilla Half-Life 2, because this is how the vulkan works in the game by default. This is a trade-off to using vulkan, however, it seems as though the longer you are using the vulkan, the less stutters there are gradually, even upon restarting the game. Any stuttering by using vulkan is likely temporary. Any potential sudden crash is also directly related to the stuttering it introduces, but upon further testing when the stutters have been gone, rare crash on map 4 does not occur anymore.