For anyone that uses demos in CSS, you may experience the problem where skipping ahead, either via GoTo in demoui or the tick slider in demoui2, causes the demo to crash and reset. I asked around on other forums and found a fix. Type host_framerate 1 in console. This will increase the play speed to a level that is close if not the same speed as skipping ahead instantly (i.e. like when using the skip functions that work in CS:GO). You can pause/resume during this until you reach the point of interest. Then type host_framerate 0 into console to stop it and return to normal. Another tip; when recording demos as long as you are either alive or in freelook spectating mode (i.e. whilst dead or in spec), you can use "Drive" when viewing the demo afterwards to look around freely and go where you want. You need to hold left click, move your mouse around and use wasd, I think z and x also help with moving up and down. This works for GO as well, and is a little less buggy there.
When I reported the problem to Steam they asked me to post on some specific forums so they could monitor the responses, so that's why I posted elsewhere. I was going to post here as well, but by the time I had decided to do that I had already received a response with a fix. I also asked many people in this community over the past weeks (including hell members) if they knew of a fix and none seemed to be aware of this particular solution.