John
I believe what you have is an HWH 310 series vertical arm room extension.
There is a manual in the coach assist section under the leveling heading on the system it's worth reading to help you understand the replacement and adjustment procedures.
If it is indeed the HWH 310 you should be able to get parts through them.
Over the years there have been several threads here on the forum on broken chains and replacement tips.
Hope this helps
Eric