Hi All. I wanted to share this to help the next Community traveler upgrading Jaspersoft.
After our upgrade to 6.2.1, while testing I discovered the Schedule screen on reports had issues that looked html/css related. We're running customized PPM themes, and while troubleshooting I rolled PPM back to the default "Teal & Grey" to find this fixed the issue while rolling back to our custom themes brought the issue back.
A deeper dive into Jaspersoft I discovered the theme set to 'default', but I noticed the other themes read something new - keyed with the release version. This tells me something's new in these themes.
Solution: Right click on the theme you wish as your Jaspersoft default theme and select "Set As Active Theme" (shown below):
This fixed our Dev, Test & Production systems. HTH the next upgrader.