If you have more than 50 or 100 avatars, the avatar menu will not allow you to see more than the newest 50 avatars or 100 if you click the expand button. Furthermore, if you scroll through your list and then hit expand, the menu crashes and the personal avatar section straight up deletes itself.
This has been a long-standing bug ever since I started playing. The excuse I was given every time I've reported this is that you guys don't want to bother fixing up the current menu since you plan to overhaul it at some point in the future. However, you are very clearly in the process of updating the menu as of the current beta (2018.4.1). Therefore, I think now would be a good time to consider trying to fix the bug since the complete overhaul is still seemingly a long way off. Its been a thorn in my (and many others) side for way too long.