Earlier versions of 12.3 IOS's had MGCP issues, and the current IOS versions are much better. I personally ran into a lot of strange MGCP issues at times with the 12.3(7)T series.
I would look at running the the latest 12.3(14)T release or a 12.4 mainline if you can. I've had luck with 12.3(14)T7 and newer in 12.3T, and 12.4(7b), 12.4(8a) seem good for 12.4 mainline so far. YMMV.
Besides IOS, you want to verify you router config is good and there isn't a router config issue getting it stuck-up. Things like having 'application mgcpapp' under dial-peers that are for PRI ports, etc.
Also, if you go to 12.3(14)T or higher you want to check your SRST and MGCP Fallback configuration after the update since the syntax changed on those commands a little. The 'application mgcpapp' changed over to 'service mgcpapp' keywords and there is a global application section now.
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The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
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Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...