Props broken in SP

Every prop in SP are acting wierd and messed up… the weights are set to 1… almost all of them. It seems all except the HL2 Vanilla Props.
They seem to want to remain still, even if you’re tugging on them viciously with the phys gun. They’re really wierd to rotate, where in some spots it’s easier than others to rotate the prop, but it can just stop rotating all of a sudden and you have to unclick and try and rotate it again…

[Possibly related] When i jump on top of the props, or hit two props together, or even just spawn a large prop around smaller ones. They give a kind of “hit by AR2 alt fire” effect and disappear…

Cheers if you know what this is :frowning:

Verify your garrysmod game files.

Er… how would I do that?