opencart products categories are dissapearing

I've asked on the support section but sadly no luck, I'm hoping someone can help and it's not a big fix.
Unfortunately when I create a product and assign it to 'jumpers' for etc it saves fine. If I go back in to edit that product it forget the category and so I have to go in again and save it. Trying to create 4,000 products you can imagine this gets annoying.
Any help would be greatful but I'd like something looked at today ideally.

My first question would be is it actually "forgetting" it, or is it just not showing in your edit panel for some reason.

If you save a product with a category then browse the category in the front end, does the product actually show in the category?

If so, it sounds like your query in the model file is not pulling correctly or the controller file is not assigning it correctly if it does.

Either way, this is not normal behavior for oc, so I would disable any mods or extensions or templates you have installed and see if it corrects it. If so, add 1 back in at a time until you find the one causing it. (I am assuming you've already checked error logs and turned on display errors temporarily and found nothing, of course).

And of course, knowing the version of oc you are using, whether or not it was an upgrade from a previous version or a fresh install, what mods you recently installed, if this is happening with all categories or just certain ones - in other words, more information - would all help.

Hi it's forgetting them as the products don't display on the store front once they are cleared.
I'm running 1.5.4.6 the latest version before 2.0
It's a fresh install and I've tried a few themes none make any difference.
I have a few mods installed, Google product feeds, options boost. Removing and re adding these doesn't seem to do much.

Are you a developer? Would you mind taking a look possibly?