Ghost activity for blocked users?

Dear Gitlab Community,

I’m reaching you today because I’m using a self hosted Gitlab v15.11.9 on a CentOS 7, with 8cpu and 16GB RAM server. I’m facing an issue concerning a blocked user, and after investigation I’m still clueless about the field “Last activity”

Here’s my blocked user, we can observe that his last activity (rightest column) is from 27/07/2023 :

But Here’s his metadatas :

Annotation 2023-08-07 142131

My question is : How come is it possible for this user to have a last activity from 27/07 ?

I also checked his information through the api :

and here’s his last event :

This user has some SSH keys but the last time they were used was 2 years ago.

Where can I found the trace of this actvity, is it a bug ? Is there any hints to investigate further ?

Thank you !