s0rexi don't know if its gonna work for everyone but for me when i change the speed to 0% and i press "goto" to the tick that i want it wont crash, try that and let me know if its working for you
This works! Just be aware that if you jump back it'll restart the demo and start fastforwarding with the slider at 100% again, causing the demo to crash, so jump to tick 100, readjust the slider to 0% and then jump to whatever tick you need.
It's still a pain to sit through the entire demo every time, and I'm pretty sure tabbing while skipping causes tf2 to crash as well. Still, it's better than nothing