https://bugs.winehq.org/show_bug.cgi?id=47666
--- Comment #1 from Sagawa sagawa.aki+winebugs@gmail.com --- I inspected this issue. It turned out that this is a window message issue. I write down here for the record.
ExEdit's WM_NOTIFY message handler for the up-down control uses NMUPDOWN's iDelta member for controlling the edit control's value. The handler assumes lParam is an NMUPDOWN pointer regardless of the notification code (i.e. NMHDR's id member).
Wine's up-down control sends WM_NOTIFY with UDN_DELTAPOS and NM_RELEASEDCAPTURE to the parent window (ExEdit side). So, the ExEdit handler gets confused when it receives NM_RELEASEDCAPTURE since iDelta value is undefined in that case. This causes resetting the value. It seems to be ExEdit's fault.
Why does AviUtl work well on native? My test shows that the control notifies UDN_DELTAPOS but it doesn't notify NM_RELEASEDCAPTURE at all on native.
Oh well.. I'm preparing a patch that demonstrates the behavior and disables NM_RELEASEDCAPTURE notification from up-down control.