In past, I’ve seen such behavior (transfer 100%, dialog stucks) most often because of some code in INIT or EXIT code of tasks that leads to some kind of infinite loop or racing condition.
When transfer is at 100% and INIT/EXIT is enabled in the transfer settings, the installation routine inside AR executes the EXIT functions of the changed tasks, exchanges the code, and executes INIT code… for me it sounds, that this sequence stucks.
So I propose first to check if you’ve changed something in that direction in the last days.
If using mapp components, additionaly I propose to check this overview in the help about recommendations how to configure the download settings depending on different mapp packages: