Mails get categorised wrong by Oulook

Dear Outlook community,

On the shared mailbox of one of our customers the users experience unwanted behaviour:

Several users have access to that shared mailbox. They use Categories to order and file all incoming mails, for speedy, and accurate handling by those same users. However, sometimes incoming mails are unexpectedly Categorised by Outlook itself, before the users see those mails. This Categorising by Outlook is almost always not according to the way the users do this, and so those mails are misfiled, and therefor lost to the users.

In my search for a solution on the internet I have found that this behaviour can be explained by the existence, and workings, of the Conversations Action Table (CAT). According to my findings this CAT is built automatically by Outlook, and contains keywords, and tags from incoming mails, and the (according to Outlook) relevant action, like assigning certain Categories, or other actions, based on behaviour by the users. However, the CAT, especially on a shared mailbox, will be filled with a lot of different approaches to mail handling. This means that Outlook, on the bases of this CAT can and will  assign inappropriate, and usually wrong, Categories to incoming  mails. This results in those mails being filed to unknown, or unexpected folders, and therefor lost to the users.

What I also found is that there is a command-line switch (/cleanconvongoingactions) which will delete, or remove, the CAT. And thus remove, among other things, the wrong way of assigning Categories.

What I want to know are the following things:

Is my reasoning, about the mis-Categorising of incoming mails by the CAT, correct?

If not, what could be the reason for this behaviour if it isn’t the CAT? (I could not find any other meaningful reason, and solution for this behaviour, on the internet)

Where is the CAT of this shared mailbox located, in the MS365 setup that our customer uses? Because I do not want to run that command-line switch on all the computers of the users that have access to the shared mailbox, only to find that the behaviour persist, because the CAT is somewhere in the cloud?

If the CAT is located somewhere in the cloud, is it possible to and if yes, where and how do I run that command-line switch, and what would be the impact of that on the behaviour of the shared mailbox?