AAM not caching JPGs - "Another request is updating the content"

AAM is caching everything but JPGs. Apparently it's bypassing the cache because "Another request is updating the content". However, it's been saying that for almost an hour. Browsers are displaying the image without any problem - it's just not getting cached by AAM.

Ideas?

wainfodecode "[V2.S10413.A34484.P65790.N37551.RN0.U0].[OT/jpeg.OG/images].[P/0.0].[O/0.2].[EH0/0].[DH0/0].[C/00.u].[K/n]"
V2: X-WA-Info Format Version
S10413: Response bypassed the WebAccelerator system.
A34484: Application: /Common/www.domain.com_aam_custom
P65790: Local-policy: /Common/www.domain.com_custom
N37551: Request Policy Node: JPEG
RN0: Response match did not supersede request match
UCI hash: 0
Object type: jpeg
Object group: images
Request served from TMM: 0.0
Request owned by TMM: 0.2
Entity hit count (local/remote): 0/0
Document hit count (local/remote): 0/0
Document not in cache.
Reason: Not applicable.
Bypass: Another request is updating the content.
Parking: Not parked.