QB64-PE v3.14.1 is now released

[RhoSigma]

Well B+,
good news I've identified the change responsible for the different behavior, it's the addition of the
_ANDALSO timeElapsedSince#(firstClickTime#) < 0.3#
part in line 14339 in file source/ide/ide_methods.bas, it's part of SUB ideobjupdate.

Bad news, that SUB handles the object updates in ALL kinds of dialog boxes and the mentioned change was required to better distinguish between single click objects, click and hold objects and double click objects in regard to catch stray clicks from falling through from one object type to another and maybe accidentially trigger an unintended action on that other object.
In short the change needs to be kept in place for now, probably a complete rewrite of that entire SUB or eventually even the entire legacy dialogs system in the future may organize things better, but that would be a lot of work and certainly happens not very soon.

On the other hand I think double clicks on list box items are pretty common anyways.