This is the same bug as 3133821 which I have closed. Text from 3133821:

In some instances, the location of the label token is not specified.

This is an incorrect one: R 313:label: lbl=[@-1,0:0='1620',<10>,0:-1]
This is a correct one: R 313:label: lbl=[@65,74:77='1620',<10>,4:0]

Code illustrating bug
-------------------------------------
DO 1620 J = K1, N
DO 1620 I = J, N
A = I
1620 CONTINUE
end