Cloudstation has lots of stability problems...things seem to work fine for a while then something changes and it stops working properly. One issue I've had (more than once) is when my laptop fails to establish a connection with the NAS from a remote network (problem #1) and then when I get back to the LAN where the sync had worked fine, it's now broken(problem #2). Sometimes I hvae fixed that by simply reconnecting, other times I've had to reinstall the client app. Basically very flaky, not something I would rely on for mission critical requirements.
My current config has been stable for a while (but has not been fully stressed with lots of remote network connections. I have tried to eliminated two possible sources of problems:
1. I do note use QuickConnect...that has proven to be unreliable (lots of people have reported problems where the QuickConnect does not work). I use a URL that points to my LAN and I've opened up port 6690 on the router to let that traffic through.
2. I do not use the the Synology Dynamic DNS service (myname.synoogy.me) for the URL. It was regularly giving me "failed to establish connection and register the IP addres" errors, and after a while went silent on the alerts, then delisted the URL. I use DynDns with the router's service...it is much more reliable and, in theory, a much better way to keep the address listing current. (Side comment...the router knows what it's address is, and updates the DynDns service when that address changes. The NAS does not know what it's external address is, so it has to ping the Synology service daily to confirm. Not a good solution, especially when the registration service is flaky.)
Net-net...I think it is a bit misleading to call this product "Beta" because they don't have a beta program running with it. If it were Beta, we should be registered as beta users, be reporting bugs, be seeing and testing bug fixes, etc. That might happened with the first Beta of this software last year, but it's hardly what is going on now. I think that Synology just slapped a "beta" tag on it to let everybody know that it is not a very stable service.