Issue upgrading ROMMON and IOS on Cisco 4500-x

Experiencing a weird issue that I haven't seen referenced anywhere in Cisco documentation.

Background: Running Cisco 4500-X on VSS setup, trying to upgrade IOS from 3.6.8 version to 3.8.6 version. Upgrade first requires ROMMON to be upgraded.

Problem: I have bootstring set to load ROMMON and the new IOS version but when I reload the active and standby switches (15 minutes downtime not really a problem in my enterprise if scheduled properly) there are issues. ROMMON upgrades successfully but when it performs the autoboot to upgrade to the new IOS the switch just hangs and never resets. System is totally down. All LEDs are off except on the power supplies which blink green. Fix to this issue is to power cycle the switch and then the IOS upgrade occurs with no problem. With 20+ locations requiring this upgrade I'd rather not have to travel to each location separated by several miles to perform these upgrades manually. Would using the issu changeversion commands rather than a straight reload for this upgrade make any difference? Is it even possible to set both ROMMON and IOS to upgrade using the issu command? Cisco documentation is vague on the subject. Anyone else encountered a similar issue before? I'm not paying for maintenance on these 4500s so I can't use TAC and our Cisco account rep hasn't been super helpful. Would appreciate any advice.