The gear RDG0206 is part of REM0043 assembly that is driving tape transport and cassette doors. Because it was made from semi-flexible material it also tends to crack during the time.
If you can hear ticking noise and tape transport and/or cassette door do not work correctly then it might be cause by cracked gear. Check service manual of your deck if there is RDG0206 (and REM0043). You can see it here: