When I download more than around 10 torrents Transmission's interface stops working properly. I get the spinning beach ball and doing anything (like unchecking a file inside a torrent) takes around 1-2 minutes. If I try checking/unchecking 10 items inside a torrent one or two will respond then I'll get the spinning wheel again for 30 seconds or so and another couple of my previous clicks will be recognized. This continues until finally all clicks are recognized after a few minutes. If I quit Transmission the window disappears, but the Dock icon continues to have the blue dot under it and I have to force quit. Maybe it would quit by itself, but I've waited around 5 minutes for it to quit before I get impatient and force quit the app. Once relaunched it works fine for a few minutes until the torrents re-establish their connections.
I have the settings for max connections set to 200/60 as someone recommended. Max download is capped at 2MB/s and upload is 1MB/s (my connection is 25Mbit/s up and down). If I only add a couple torrents this issue doesn't occur, however I don't think having 10-20 torrents active is all that out of the ordinary. In the past (Many versions ago) I've had up to 60 torrents active and did not experience these slow-downs in the interface.
The rest of the computer continues to respond normally. Transmission is normally using around 4-5% of the CPU. When the issue occurs, the CPU usage drops to zero, and then when the spinning wheel disappears, the CPU usage jumps up to around 10-15% almost like it's catching up with whatever it was supposed to be doing when it froze.
I know this has something to do with some limit being hit, however I can't figure out what that may be. I'm connected directly to an AirPort Extreme router ver gigabit ethernet. The outside connection is through FIOS 25/25 which works fine for all other network related duties and the machine is an 2.8GHz 8 core Mac Pro. I'm saving files to a RAID 5 array connected through FW800 so the RAID isn't all that fast, but I'm only downloading at most 2MB/s when this occurs. It's not that big a deal as I rarely have to interact with Transmission due to the watch folder, however when I do, it's really annoying.