i have had games i made in 4.8 and update to 4.10 then to 4.11 break. The upgrade isnt perfect as the warning they give you states. Things that worked a certain way in one version may not work the same in the other. sometimes work arounds are done in an earlier version to account for bugs in that version that then are patched out in newer versions and cause new bugs, if you dont understand this im sorry for you. Sometimes you update engine version with no issues. sometimes it causes your entire project to be easier to be redone from scratch. Layer that on top of the fact the dev kit is custom coded and when its updated to the new version all that custom code would have to be redone compounds the issue. it isnt rocket science to understand how a huge jump in version could cause a catastophic failure in a complex system…