Hey Anton,
glad to hear you already got it resolved.
Filesystem hooks (i.e. AV-Scanner, etc.) would have been my first guess, or possibly a slow harddrive with the files being cached when accessed after the first usage.
Apart from that there’s certain other things that we’ve seen that can slow down the filesystem, like NTFS Last Access Time Stamps being enabled (which causes a write every time a file is read), but these usually create a constant slow-down, not once per file.
We’ve definitely seen lot’s of reports of antivirus software affecting performance, so it can be beneficial to mark your project or engine directories as exclusions for any running on-access scanners.
I’ll mark the ticket as resolved.
Best,
Sebastian