So I own a media tumbler, the same one used by Rybonator in this video: https://youtu.be/LNGL1rUAqD4

Except, the media he uses in the tumbler (those wooden blocks), is unavailable to me at this time. It was hard to figure out what to use and I tried to do a lot of research on it and found that a few people use non-abrasive ceramic balls.. The problem was that no one included links or sizes. I ended up purchasing these: https://www.amazon.com/dp/B09KH3NZM5?psc=1&ref=ppx_yo2ov_dt_b_product_details

So I attempted to use the tumbler but noticed pretty quickly that everything kept moving towards the middle and essentially staying there, thus not getting polished. Is this because of the media I used, was it not heavy enough or large enough? Or is there some other issue?

Thanks in advance, I really want to open a shop because I have some really unique custom dice but I need to work out all the kinks first and this is one of the most confusing for me.

Edit: Thank you everyone for your help. I did the reverse funnel and soap water and that helped but the actual problem was my own stupidity. I didn't screw in the machine all the way when I put it together. Thought I did but I didn't, so it wasn't vibrating right and is also now waaay quieter. Thanks again, I appreciate it.