Sorry this one got missed.
At fist glance there appears to be something else closing the connection, as 20 seconds is very aggressive and we wouldn’t (or shouldn’t) time out that early.
The GET command you are running would be quite computationally expensive, however it should return a result. Are you able to let me know if anything changed that started causing this issue, especially if you have just upgraded your Octopus Server (original and upgrade versions would be greatly appreciated if this was the case).
One option that may help work around the problem would be to only grab a certain subset of variables and then iterate over than number to make sure you get all the variables. For example:
Hopefully that helps relieve the immediate problems until we can identify the root cause.