Alright from what I am understanding from both
@UnknownFellow and
@softiethefem is that the user list of online users, not the search user list, keeps resetting after a set time and yes depending on your device, {mostly on phones after this update}, and what actions you are doing, {such as opening profiles or clicking actions}, it does happen.
I should say that this is not a bug but a feature that was added/became the reason of some coding changes.
Chat_log and system_clean are two different and the two main functions that run every three seconds by default.
They are what needs to have for any new messages, kicks/bans, or literally anything to happen.
They "reload" / refresh the chat without needing to reload your page.
I'm not going to go deeper into the code for why it happens and the code behind it but I will say that it's not going to change especially with a chat this big it needs to reload many times per minute.
TLDR: It isn't a bug just a feature that shows everything new {such as messages and staff actions} so that you don't need to reload your page for each thing.