Loop of length 6 starting with a string of length 6
found after enumerating 34 derivations:

.aba.abb
	rule aba -> bbb at position 0
.bbb.abb
	rule bab -> aba at position 2
.bbaba.b
	rule bab -> aba at position 3
.bbaaba.
	rule aba -> bbb at position 3
.bbabbb.
	rule bab -> aba at position 1
.bababb.
	rule bab -> aba at position 0
.abaabb.