504 Gateway Timeouts generally means that the communication between the client and server is lost.
1. It is possible that you are trying to get a large amount of data which recycles the application pool or breaks the database server
2. Custom controls which cause stack overflow
3. Server side issue due to some other reasons - fixed time for restarting etc.
The issues with the Themes could be result of some sync issues in cases of web farm.
It is hard to tell you what the exact reasons for this behavior are.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items