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:
Disassembly of this type of drive mechanic is slightly complex because you need to use soldering iron to de-solder motor contacts from PCB board. But it is not so complex as it looks like. Just follow instructions in service manual.
The gear RDG0206 is used in assembly together with REM0043 gear that might tend to crack too. It also available as 3D printed replacement.
You can see demonstration of replaced gears at video bellow
The part is compatible with following devices:
RS-BX501, RS-CA1060, RS-CH404, RS-CH909, RS-DC8, RS-HD505, RS-HD505ES, RS-CH510, RS-HD515, RS-HD515PPS, RS-HD75, RS-HDA710, RS-HDA710PPN, RS-TR170, RS-TR270, RS-TR373, RS-TR474, RS-TR575, RX-DT75, RS-TR777, RS-TR97 .
It might work also with other devices – just check your service manual.
Available for purchase – go to shop.