Product Type page is empty and Add New Product Type throws an error

Product Type page is empty and Add New Product Type throws an error

Within the Asset Management section of Admin, if I go to the 'Product Type' screen, I get no list of product types, just an empty white screen [screenshot attached].
If I click on 'Add New Product Type', although the new product type form does show, I also get an error at the bottom of the screen [screenshot attached].

However, our previously created product types are still there - if I add a new product, the Product Type dropdown is correctly populated [screenshot attached].

I think this started after we applied the most recent patch to update to build 9309 - I can't be 100% certain though as I haven't had a need to go into the Product Type screen for a while.

We've consistently reproduced the issue using different browsers, different PCs and different technician logins. We've tried restarting the SDP service and the whole server, problem is still the same.

I have tested a fairly large sample of other screens and functions within ServiceDesk and can't find anything else which isn't working.

I can't see anything obvious in the Windows event viewer or the ManageEngine logs folder, but may not be looking in the right place.

Any thoughts or suggestions gratefully received.
Thanks,
Chris.

EDIT: It just occurred to me to look in my browser console to see if that would show anything helpful.

When trying to display the Product Type list, Firefox has 2 errors: "TypeError: div1 is null" and "XML Parsing Error: no element found....", and Edge says "unable to get property 'id' of undefined or null reference".

I've attached screenshots of the full errors.

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