I did some thinking and remembered that I downloaded all symbol files for Windows 7, 8/8.1 and 10 (up to a certain build) and until now have a symbol folder of ~73GB. Last time I checked it was around 55-60GB which is a while ago, it may very well be that somehow some symbol files have become corrupted. Ironically, I don't have time to do a simple check for corrupted symbol files and replace them if any, even though I'm not employed at the moment.