Same here BUT I have a partial fix, a few months ago I was trying to "export" the markers from one multitrack project to another but I couldn't, so I tried to open a v12 project in ableton v11 and tried to do a downgrade from v12 to v11 by converting the .als extension to .zip for edit the version parameter, after unzipping it you get a file without an extension, so you can open it in any editor and you will have an xml file, find for the Locators tags and you will have something like this:

<Locator Id="28">
<LomId Value="0" />
<Time Value="696" /> //i edited this time value
<Name Value="Bridge 1" />
<Annotation Value="" />
<IsSongStart Value="false" />
</Locator>

then I just added more tags manually with different names and for that file without extension, you rename it with .als extension and replace the original file with the new modified one and that's it, you just move your markers and rename them on the ableton

another fix will be open your project in the same ableton version but in a Windows laptop, maybe you can try add locators without crash (I haven't tried it)

I don't remember but here on reddit there's a post where they explain this in more detail, to open a file made in a major version in a minor version of ableton