When a HEAD request is issued for a file under /content/dam, then instead of returning the correct headers back, it issues a 302 redirect to the same file with "/" appended to the end of the URL. For example, this HTTP request:
HEAD https://www.geometrixx.com/content/dam/test.jpg HTTP/1.1
Responds with a 302 redirect to:
This is a known product bug CQ-4221520.
The fix is included in AEM 6.4.
Cumulative Fix Packs (CFPs) for older AEM versions: