Client bridge not stable

[mkc2lr]

I successfully configured my TP-Link WR741ND as client bridge with gargoyle in 5 mins after unsuccessfully trying this with dd-wrt for several days.
Unfortunately the connection breaks down after a while (between 30 mins and 3hours). If I reboot the client, it works again. There might be a correlation between the traffic activity and the disconnection. I'm under the impression that after a long time of inactivity, there's a disconnection. Is there any power saving function causing this?
I'm using 1.3.10. Thanks for any hints!

[mkc2lr]

I solved the issue:

I set the AP to WPA2 only instead of mixed and I reduced the TX power on the client. Works since one day now.