Upgrade issue on Chrono v4

We are preparing to update one of our sites from Joomla 2.5.28 to 3.3.6 (3.4 apparently is too buggy still).

We were updating all our components including Chrono to the latest versions. When we did, I discovered I can' edit any forms in Joomla 2.5 anymore, if I click to Wizard Edit or just click any form name to Edit, it shows a blank white page. Forms seem okay on the frontend so far.

We updated Chrono to v4.0.6 component, 4.0.3 mod, 4.0.3 plugin.

Can you help? Don't want to revert to backup unless we have to.

Thanks.

Hello Umbrella,
I'm not a Chrono professional, but after checking your new post, I think that the following links may help:
How can I upgrade from ChronoForms v3 to v4?
P.S: I'm just an automated service😉

We weren't upgrading from v3 to v4, we were upgrading from 4.0.3 to 4.0.6.

Could we just grab some chrono files from an Akeeba before the updates and replace the ones on the site?

I think I see the problem now - there are versions for 2.5 and 3 - this was not clear to us. I assume the v3 Chronoforms stuff just breaks on Joomla 2.5. Are we stuck restoring from backup?