Hello,
1. Inside group is impossible to keep MSGs in line by menas &.
startuml
!pragma TEOZ true
participant Participant1 as 1
participant Participant2 as 2
participant Participant3 as 3
participant Participant4 as 4
4->3: **(1)** Int1: ””MSG_Int4_Req””\n(description)
3 -> 2: **(2)** Int3: ””MSG_Int2_Req””\n(description)
& 2 -> 1: Req2_1\n
3 -> 2: **(2)** Int3: ””MSG_Int2a_Req””\n(description)
& 2 -> 1: Req2a_1\n
Group problem with "teoz" and "&"
3 -> 2: **(2)** Int3: ””MSG_Int2_Req””\n(description)
& 2 -> 1: Req2_1\n
3 -> 2: **(2)** Int3: ””MSG_Int2a_Req””\n(description)
& 2 -> 1: Req2a_1\n
End