I have one 2801 (IOS 14.4.15T8) with one BRI the problem is that many calls (inbound ou outbound) trough BRI gets dropped
network-clock-participate wic 0
network-clock-select 1 BRI0/0/0
no ip address
isdn switch-type basic-net3
isdn incoming-voice voice
isdn static-tei 0
Usually in another configs i use static tei with no problems.
Layer 1 and Layer 2 are UP in BRI with no calls.
I see a lot of %MARS_NETCLK-3-CLK_TRANS in logging when calls are dropped layer 2 goes dow.