Photos hangs when dragging certain photos/videos from shared to normal album

In Photos on macOS 10.13.5, dragging items from a shared album to a normal album works fine unless Photos detects one or more of the items already exists in the local library, at which point competing dialogs cause Photos to stop accepting user interaction in a way that can only be resolved with a force-quit.

Another user reported this problem in December with 48-53 people reporting the same problem. Several people in the previous discussion were easily able to reproduce the problem. But that thread was closed before anyone offered a solution. So as the site instructed, I'm asking it again as a new question. The screen grab above is mine. The other user's excellent detailed description of the problem is below. If anyone can offer a way to do this without me manually avoiding duplicates, I'd be grateful.

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macOS 10.13.2 using Photos. I am importing 1600+ photos in a shared album to a local album. Some of those photos and videos were already "Saved" using my phone. As a result some random photos and videos are already on the local Mac and will be "duplicates" if re-imported.

After dragging, say, 100 photos for import, a modal popup comes up advising me, "Add 100 photos to Album "foobar." It is a "MODAL" popup for the Photos app, locks everything in the Photos app so that clicking anywhere in the app results in a system beep, and it has a minimize light (yellow, but the close (red) and maximize (green) lights are grayed out, so there it no way to close it.

If there are no duplicated photos in the drag, then after they have been imported, that modal popup will disappear, and all will be well.

HOWEVER, if there are any duplicates, a small window will pop up BEHIND the modal popup, and it shows thumbnails of both the importing and the existing photos, and asks, "Would you like to import the following duplicate photo [or movie] ? It has CANCEL and DON"T IMPORT and IMPORT buttons with a checkbox for "Apply to all duplicates" -- HOWEVER, it is impossible to click on that window -- the initial modal popup has full control and it does not let the user click anywhere else -- it just waits for a choice that is impossible to make, and clicking anywhere just results in a system beep.

It is a program hang. The only way to get out of this is to force-quit the Photos app, then restart it. All positioning is lost, I have to re-locate the import point, and figure out how to skip the duplicate, and as soon as there is another, it will hang again. Over and over. I actually have more like 6000 photos to import in multiple shared albums so it will take forever due to numerous duplicates over 3 years of more favorite photos.

Am I doing something wrong or it this a bug that an import is able to hang this program? I hope it is me, but fear it is a bug with no good workaround. I am amazed no one has raised this issue yet that I have been able to find. I am rather annoyed.

If anyone has a solution or workaround I would appreciate it.

Thanks!

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P.S. - In case an ambitious Apple employee is reading, the desired behavior when Photos detects an item in the shared library is already in the local library would be to automatically add the existing local copy to the local album and only attempt to import shared items that are NOT already local, without requiring any user attention. In case a user really wants to clutter their HD or iCloud account with unnecessary duplicates and Apple wants to help them do that, just add an "Avoid importing duplicates" checkbox in the preferences panel which is on by default. Also, reconsider whether that "Add X Photos to Album..." modal dialog really needs to block all user interaction. If so, find a way for subordinate dialogs to accept user interaction even while the modal dialog is displayed.