First observed on SDK 4.20.00.35 (ble5stack_2_01_03_00)
using CC2652R1 and multi_role. This issue is observed when the crypto driver is stressed in order to reproduce (i.e. encrypted connection with 10ms or less connection event - several packet with encrypted data has to be exchanged at each connection event)

The issue causes the connection to be terminated by the peripheral. The peripheral basically does not answer to the connection event. When looking into the peripheral code, we see the error code LL_STATUS_ERROR_CONN_TERM_DUE_TO_MIC_FAILURE.