imap problems on Kmail

[maximus]

After having been offline for a few years I am back and had to update from no longer supported Mint 19 with kmail 5.7.3 which I have been using with a new imap account. Previously I had pop accounts. With the new imap account kmail 5.7.3, on Mint19 no less, works fine. However with updated Mint (21 and 21.2) and kmail from their repos it doesn't work with varying degrees of difficulty / problems.
So I eventually end at Kubuntu LTS Jammy after trying other KDE spins with similar problems, and encounter more of the same.

Problems:

• kmail repeatedly and rapidly rescends the same email. Resolved (in some instances, with vary dergrees of efficacy) by removing or pointing filter to local folder only or not using filter at all. Sometimes problems with inability in removing "unrecognized filter" period. (wording to that effect).
• in some circumstances when I've worked around the sending problem, upon deleting sent identical emails from inbox the mail in question appears greyed out and is inaccesable by kmail but is still there and accessable by others ie epiphany, or previous kmail on Mint19

After many, many attempts with clean (and I mean zeroed out drives) and re-installs with various iterations of Mint (I'm aware they've left KDE behind) and other KDE spins and especially of note Kubuntu,
as well as much searching of forums, it seems clear there is a problem at times (and atm) with akonadi and imap.

Is there a known problem and or solution to this?

I have a need of the security offered by the Ubuntu platform and KDE, and not the expertise, and certainly not current experience to get any further by myself.
(ie what's with (correction: Snap located?) FFox doing showing up during boot? ignore that for now...)