Beside the available resources from the server it's possible (but IMO rather unlikely whereby you could check if there are any proxy-server between your browser and the Qlik server) that there is a network-delay (if so it should be noticable with nearly all applications and not only a few).
Another more probable cause could be that there is any section access which might break some calculations. The easiest check would be just to disable it.
Furthermore take a look on the used releases from the client and the server - both should be the same.
Hi @Vegar we are also having a similar problem. We are considering increasing the RAM but this will obviously cost money. Is there a way or test to find out if increasing RAM would actually improve our performance before actually committing? We have very large datasets