Weird PMS behaviour after latest upgrade of CB

We have been using PMS Uddeim plug in etc with CB for over 10 years now with no issues. Two days ago I updated to 2.5.0+build.2021.02.01.21.20.37 and since then some users do not receive alerts when a Private Messages are sent to them. Weirdly some do and others don't.

Of course have tried all the fault-finding I possibly can from switches in Uddeim (we are on 4.0) - you name it, even mail server logs to see whether messages were rejected, but they were never sent to begin with.

And yes once again I tried all the usual reasons it could be, Front end user switches, back end switches, both Uddeim and CB configuration, mail server issues, Joomla mail send etc...

I have now exhausted every conceivable reason - does anyone have any idea what it could be at all or what else i can try?

CB forum tells me its not a CB issue.

I switched on error reporting and found this message - is this perhaps indicative of the issue?

Warning: Declaration of getuddeimTab::sendUserPMS($toid, $fromid, $subject, $message, $systemGenerated = false, $escaped = false) should be compatible with cbPMSHandler::sendUserPMS($toUserId, $fromUserId, $subject, $message, $systemGenerated = false, $fromName = NULL, $fromEmail = NULL) in /home/membersweb/public_html/components/com_comprofiler/plugin/user/plug_privatemessagingsystem(uddeimpms)/pms.uddeim.php on line 252

I'm starting to get this too - did you work out how to fix it?