When uploading new version in document libarary to an autocad file (dwg), the mimetype would chnage from correct Mimetype: AutoCAD Drawing to incorrect : Mimetype: Binary File (Octet Stream). manually amending the mime-type within the file properties in the Alfresco share, restores the preview correctly.
This was tested replicated on 5.2.2 and 5.2.6.
1) log in to share>site> document library
2) upload StartTrek_1.dwg file (attached).
Please note, this is also happening with Microsoft Project files (MPP). I have uploaded example MPP. Everything else behaves same with MPP, new version has mimetype of mimetype=application/octet-stream
3) Validate mimetype property displays the correct value: Mimetype: AutoCAD Drawing ( screenshot 1)
4) Select Upload New Version action and select file StarTrek_2.dwg (attached)
Node's property shows: Mimetype: Binary File (Octet Stream) - (screenshot 2)
The Mimetype should remain as AutoCAD Drawing