ok… i checked, and two or three Ater TP timeslots must be reserved for Frame signalling, Qmux etc.
Those reserved timeselots are recommended to be selected among the timeslots 0, 14, 15, 16 or 31.
No mention about bad quality. But if you do not follow the recommendations, it might lead to degraded quality 🙂
About the call drop troubleshooting, it is the job of radio engineer, it requires experience on parameters, QoS monitoring, drive-tests and radio propagation. It is not something I can summary in one post… sorry.