When using the water volume spline things such as lake, ocean etc, any landscape streaming proxies they touch while having effect landscape turned on will check out those proxies.
This causes havoc with multiple people working on a map with URC as it will circumvent the check out protection and lets multiple people check out the proxies, and this can be quite a technical mess to get out of and involves using URC commands in powershell which itself can be dangerous to the casual creator.
This really needs to be addressed before people destroy their own projects and essentially get locked out.