It's likely Windows Defender, which blocks on read I/O to scan files. Verify by adding a folder to its exclusion list, though this isn't helpful if it's a deskt

It's likely Windows Defender, which blocks on read I/O to scan files. Verify by adding a folder to its exclusion list, though this isn't helpful if it's a desktop app. The difference is most noticeable when you're reading many small files.