Creeping In Gear or Does Not Stop or Secondary Won't Stop Turning or Hard to Get in Gear
Could be several things, most common is a bad bearing in the primary clutch or alignment, this linked article will help you find it then let me know what you find or take the same picture as in article and email it to me so I can see what you got going on. Also, if this started when you put a new belt on, it can be that the fact it is new and this wider than your old, then with a slight alignment issue your narrow old belt cleared a new one does not, sometimes once broke it can go away.
This tech article goes in detail or if you like a visual better click the you tube link
New Video about this https://youtu.be/Yoi_YELCd9E