OH2 - DateTime items change format when they get updated

Im sure this has been raised before, but i cannot find it ;-(

When a sitemap ( im using Classic ) is loaded my DateTime items get displayed as i would expect, but as soon as an update comes the formatting changes completely.

This is the Item:
DateTime GarageLedStairsMotion_LastUpdate "Garage Stairs Last Motion Detected: [%1$td/%1$tm - %1$tH:%1$tM]" <clock> (gMonitorUpdate)

This is how it is displayed when the sitemap first loads:

but as soon as the item gets updated, the formatting changes to:

The rule which updates the item is:
rule "LastGarageLedStairsMotionUpdate" when Item GarageLedStairsMotion received update then postUpdate(GarageLedStairsMotion_LastUpdate, new DateTimeType()) end

Any ideas how this can be fixed? or what im doing wrong? is it a known bug?

I think I saw this mentioned previously as a know problem with an Issue created to fix it, if it hasn’t already been fix.

Right here for example.

Note that this is the Basic UI, not the Classic UI.

thanks Rich and Kai.

Ill watch that bug ticket.