Apparently there is a setting to turn this off: Go to Settings, Customs, and untick "HS Code & Description auto-lookup". Didn't know about this, or whether it's a new feature or not, but it definitely works.

Even worse is it you enter a customs description (such as B2B Sale - Reverse VAT). If you try to delete that on a sale to a consumer, the comment is still included AS Royal Mail website does not save an updated empty field.

I agree too.
We push orders to C&D from our system via the API and we have carefully entered HS codes and customs descriptions for each one of thousands of products into our system, which accompany the API call. This worked fine for ages and made for a very efficient shipping process.
Now we have to check and correct every single item on an international shipment and this takes a lot of time. Pretty much every one is wrong. Today's first example: a sealing washer showed up as a "dog toy". It isn't as if the descriptions C&D provides are even remotely accurate.

By all means suggest descriptions if we haven't provided one - that might be helpful - but PLEASE DO NOT overwrite our customs descriptions. If we provide one and it is wrong then that is our own look-out. If a customs description could be derived accurately from a HS-code, then customs would not require a description.

And if you do suggest a description where none is provided, please highlight that item in the list so we can check the suggestion before continuing. That way we can assume that if nothing is brought to our attention, we can just proceed to print the label.

Honestly, I would prefer no action at all other than flagging when a description is missing.

100% absolutely. Don't auto-update, unless the field is blank. Or at least, give us an option somewhere in the settings to enable/disable this feature.

Agreed, it's both frustrating and not time efficient correcting each time.

I did try to roll with it, and not correct it. I've discovered, at my expense, overseas customs also don't accept your basic auto descriptions, especially when I'm sending multiple items all with the same description but different weights and prices. They become delayed or sent back to me as a result.

The HS number shouldn't be an auto input for item description. Would be more efficient if it displayed the HS number that we enter for our products, or what is being exported from 3rd party selling platforms, ebay, etsy...

Absolutely agreed, there's no need to autofill to an incorrect commodity code and description.

Even when the product is presaved with the correct code, during the Add Products dialogue box it will auto change to something similar often several times despite deleting and retyping.

This is driving me mad too, everything I process seems to be a camera strap. I usually catch it and change it back again but they do slip through when I'm sending 40 odd international parcels a week.