PEN Short Squeeze, page-110

uranium spot price will generally fall a little at the end of the month mostly due to carry traders that have agreements with some producers to purchase future pounds at the end of month closing price and so these traders will trickle some of these pounds into the spot market a day or two before the end of the month to lower the closing price. volumes and price movements are normally relatively small, so it's really just a little manipulation by the carry traders to get uranium that they are contracted to supply to utilities a little cheaper.

Justin Huhn (YouTube channel: uranium insider) explains this in detail - see episode 71