Rewards do not transfer to Uphold in full

For almost a year, when the month ends I receive a deposit from Brave in Uphold corresponding to my reward, but only 0.25 BATs or less are transferred.

I already have 2 BATs accumulated in the browser that never get transferred to Uphold. Why? Why do I want to have two BATs stuck in the browser? I need to transfer all the BATs, for that I have the option to see ads activated.