Answer
Check for a regional-settings mismatch between the affected user's Windows/Excel configuration and what the exported data assumes — for example, whether Excel on that user's machine expects a period as the decimal separator while the exported data uses a comma (or vice versa), which is a very common cause of exported numeric or date data looking garbled for one user but not another on the exact same export. Comparing the Windows regional format settings between the working and non-working user's machines is the fastest way to confirm this as the cause.