Hi, Once MSG1 fails UE selects the same preamble group for the next mSG1 transmission, in the preamble group it selects randomly preambles for next transmission, so it may select same preamble in random manner.
UE will select preamble group based on the msg3 size and path loss, then if msg1 fails then pathloss is more so it should change the preamble group , because existing preamble group is having more path loss but UE selects same preamble group is mentioned in spec why?
Say e.g ENB given some random preamble to UE1 to do RACH, but in -case same preamble is selected by UE2(preamble given to UE 1) and doing RACH . In the above scenario ENB will not give any CRM message to UE's so how contention will be resolved for UE2?