different behaviour when osmocom-bb runs on c155 and c115

When running the layer23/mobile host application in combination with layer1 firmware on a c115 (compal_e88 based) I can easily connect with a network (when using Sylvain's test trunk, which supports the SIM very well!). However, running the same code on the C155 (compal_e99 based) the phone refuses to connect to the network and keeps scanning ARFCN's. Is there any real difference between these phones except for the LCD's? In rffe_dualband.c I see a remark about the value of SYSTEM_INHERENT_GAIN that has been measured by Harald on the C123. May that be a different value for the C155? Is this a problem observed by others, or is there a workaround?