Current beta firmware release 31824 is not working correctly with Gigaset C610IP VoIP phone.
After 30 minutes there is a long signal on all VoIP accounts including gigaset.net and problem with SIP registration.
I was trying to increase and decrease TCP and UDP session timeout values using telnet command but without positive results.
There was no problem with Gigaset phone with the same configuration in older Draytek beta firmware.

Internet Access used: only WAN 2.
Model: Draytek 2830Vn Plus Dual Band.
Firmware: v2830_AnnexA_r31824 BETA (downloaded from ftp.draytek.pl).
Gigaset C610IP firmware: 03/2012 (version 051) - latest.