Hello,
I have noticed a bit of an unexpected and annoying front-end behavior that occurs on that Sample Add screen now that we have moved from v2.0.0 to v2.4.0. 
When clicking on a Reference Field cell box on the Sample Add screen (doesn’t happen on other screens that we’ve noticed), there is a slight pause while the system is loading the DisplayList for the field.
However, the unexpected and annoying part is that when the search call finishes, it will De-Select the user from the reference field cell box - forcing them to re-click into the field to search. This does not occur EVERY time, but does occur very frequently and seems to occur more for the Sample Type, Analysis Spec, and Analysis Profile fields.
Once it happens once for a cell, it will not happen again for the same cell box until it triggers for a different cell box - so we have a workaround. However, it is severely slowing down the sample reception staff.
The behavior was not present in v2.0.0, but seems consistent for Mozilla, Chrome, and Edge in v2.4.0.
Is there anyone who has tinkered with that screen’s JavaScript enough to know what might be causing such a behavior?
...or does anyone know just a convenient way for me to turn it off? hah
and the new UID widget looks great!