Ebucks tier points missing.

I received my monthly ebucks allocation today and see that I have dropped to a level 4 from level 5. I made sure to meet all requirements to earn level 5 tier points, however I see points missing after the allocation for last month. This has happened a few times before and ebucks customer care is a nightmare to liase with. Their answer is always a 'sorry, we cannot help you' after escalating the issue. I then started taking screenshots of my points at the end of each month. I see that on 27 April, I had a total of 12500 which took me to level 5, how do points disappear from certain categories after the month is over? Could someone please assist me.