Checkout - removing products which return

-- HikaShop version -- : 4.6.1
-- Joomla version -- : 3.10.10
-- PHP version -- : 7.4.30
-- Browser(s) name and version -- : Firefox & Chrome
-- Error-message(debug-mod must be tuned on) -- : No
Console no Errors

I have done various updates to the site in the last week.
I now noticed when you remove products from your checkout, the screen refreshes and the product returns. If it is the last product, the screen refreshes back to the checkout with the product in. In Firefox, it started displaying the text 404 in the checkout product rows and then refreshing to full checkout. If you remove the item a second time, it can disappear.
If you remove the items through your cart, there are no problems.
If the user is logged in, everything performs normally. It appears to be occurring in guest checkout.

I have new cookie control, but turning that off does not seem to alter it. I have turned off JCH Optimise to ensure that not interfering but noticed no difference. The Console is not reporting any js errors.

I have not noticed the issue until it reached the live environment, so advice as to what could be conflicting would be very much appreciated.

Thank you for the quick reply.
As you point out it was the cache. I had turned on the page cache in JCH Optimise and while it didn't list the page as cached, it must have been. I have told it not to cache that menu option and the checkout has started working in both browsers.
Thank you for the very quick response!