I am getting this crash often when saving my root map (that have sublevel). Sometimes it happens everytime when saving, then suddently saving might again work normally. Very strange issue, didnt have it in 4.12 and ealier engine versions. Cant reproduce in test project.
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Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000010
Sent crashreports with MachineId:F87B756443F95CE9986941A672FE5264
Hello ,
There seem to be a multitude of errors related to missing pin connections, many “accessed none” errors and the sort. I would suggest looking through the log and attempting to sort these out. An access violation crash is the result of referring to a null reference of some sort. It’s likely related to one of these many errors and warnings, if not all of them.
Okay, thanks I will keep looking what could be causing it. Found so far only killbp and fallbp with accessed none, but those dont exist during map saving. But could be definitely something wrong in some blueprint I have placed on map.
We haven’t heard from you in a while, . Are you still experiencing this issue? If so, have you had any luck finding any of the root problems? In the meantime, I’ll be marking this issue as resolved for tracking purposes.
It seems to be related on blueprints with instanced mesh components. I had some blueprints forgotten there with zero instances added (the actors were made with rama’s plugin, now converting those under instance tool by Mary - since it support hierarchical instancing. Noticed it left the old actors undeleted). After deleting those, the levels mostly save correctly. But getting also similar crashes when duplicating my own instanced mesh component blueprints in viewport. I will look more into it, but the worst is gone at least. 
Been trying to repro the duplicate crash on separate test project, but no luck yet.
Hi, this issue is hierarchical related. Noticed that got crash everytime after copying actor with hierarchical component into another level.
Maker of instance tool - , also confirmed it saying “the internal tree did not rebuilt correctly” which seems to be engine related:
Hope you are looking into it. Even mostly can avoid the crash now.
I’ve left a comment for to report the issue if he/she hasn’t already. I tried searching for a bug report related to this issue but couldn’t find anything and without a report for it, it’s not likely to get fixed.