Many apologies if this has been discussed elsewhere alreday!

I have for the last 18 months or so been flying with KLM through work on what I understand to be seaman's tickets. I gather that these only provide 25% level miles but there seems to be a great deal of inconsistency in the process as the vast majority of my flights have been granted 100% miles and on my last 3 trips to Houston from Amsterdam I have received 25% on the outward journey and 100% on the return flights. In addition, a work colleague (both working onboard the same ship) who has been on the same flights, booked through the same agency has received 100% miles on all flights and has reached gold membership whilst I am still silver (and he has missed one trip so is 2 flights less than me). Is it normal to find such inconsistency in these programmes?

Again apologies if this has been asked before or if this is a stupid question but I have little experience of frequent flying and these programmes.

Thanks
Ian