I get asked about the Fostex R8 almost on a daily basis , so will put this here as it will solve about 80% of peoples problems
The R8 uses two reel motors on which both have pressed on them a black plastic pulley, it relies on being pressed on there is no locking pin etc.
Many people have been using sticky old Ampex tape or just using their machines a lot.
In the end the pulley starts to slip, it may work half way through the reel and then slip or it will not work at all forward or backwards.
The main solution to this is get a new pulley (some man in Italy was making a 3D printed version)
I now have metal pulleys in stock that solve all the problems
Also I am hearing more people with capstan pulley problems so now they have been made as well