Anytime I try to dematerialize/rematerialize with my handbrake, it does nothing whatsoever. Whenever I try to use the flight panel, it give me a message saying how my TARDIS is already in flight, and I get a similar message whenever I try to leave through the door. Dying and respawing in the world to go find my TARDIS won't work because I flew somewhere really far away from spawn and I can't remember where exactly I went. Please help if you can, preferably if you've encountered this issue before and know how I can resolve it without losing all the hard work I put into my TARDIS for the last few days.

It happened to me quite a few times and there were quite a few ways to fix it. You can spawn another TARDIS and blockdata it to have your TARDIS exterior ID. You could also find your TARDIS exterior where it supposedly landed and break it and then teleport to your TARDIS Interior and try to dematerialise it.