Cannot add products to cart since one click upgrade

[dragon_sa]

I upgraded my shop to 1.7.7.4 via oneclick upgrade and now in my shop a client cannot add products to cart, in my pos module I cannot add products to cart, that gives me a message not enough quantity.

I had my shop configured to allow ordering with no stock,, because 90% of our products are custom made and manufactured when ordered.

I went through and added 50000 quantity to all my products and I still cannot order in the shop or the pos module(which still gives me the same error), I dont want to go back to 1.6.5 because that uses php version which is no longer supported and deprecated.

How can I start to fix this please.

Edited June 14, 2021 by dragon_sa (see edit history)

[dragon_sa]

I tried upgrading to the new 1.7.7.5 and that also gave me no joy, even disabling 3rd party modules and overrides, I have been forced to rollback to 1.7.6.5 and everything works again and site performance has increased dramatically.

My only problem is I have lost all the product combinations and pricing I had added and changed while in 1.7.7.5, so back to the hours of redoing all that.