So, I'm not sure if Jaxx already fixed that, but there was an vulnerability which let you get your backup seed from the wallet files. And since they didn't care about it, maybe it still works.

Can you backup your Jaxx folder and try this? https://vxlabs.com/2017/06/10/extracting-the-jaxx-12-word-wallet-backup-phrase/#demonstration

Or just try what I said above as it won't risk your current wallet anyways (you are just copying the folder and pasting it in another device, where Jaxx works).