net-im/twinkle DTMF stops working after about 30 seconds. This bug is know upstream and a patch is available. A patch is also available for a known to/from/subject field clearing bug.
Created attachment 101080 [details, diff] invite 4xx to/from/subject clearing patch
Created attachment 101081 [details, diff] DTMF timeout patch
added to twinkle-0.9-r1. Thanks refering to the web page where the patches are is enough.