Understanding Society User Support

Hello, I am using the employment history data and am interested in reasons of changing jobs. Am I right that a question on reasons for leaving a job is MISSING in waves a-d of the UndSoc for one job spell, which is indexed by variable names with nxtjb? I guess this is the next job spell after the one recorded at previous interview.
If I got the allocation of variable names to spells right, the sequence of spells is as follows:
w_empstend/w_jbend - the first spell (recorded during the previous interview), the question on reasons for leaving is w_stendreas/w_jbendreas
w_nxtjb - the next employment spell, the question on reasons for leaving is w_nxtendreas, but it pops up only in wave e and later.
w_nextstat1 - the next spell, the question on reasons for leaving is w_reasend1
w_nextstat2 - the next spell etc., the question on reasons for leaving is w_reasend2 etc.

If would be very helpful if you confirmed that this question is indeed missing in earlier waves or told me the variable name, if I am wrong.

With kind regards
Maria Pavlova