This is supposed to go to customer support so I don't know why they sent you back here but I know what it feels like being sent back and forth so I will try my best to help you. By doing a little Googling I found that error 403 tends to be something that doesn't permit you to connect to something. I also have a question, where are you seeing this error? Is it in the launcher or on the website?
Anyways, try to disable windows firewall before purchasing (but remember to turn it back on afterwards). If that doesn't work then try to do it while connected to a VPN if you have access to one (You can probably get a free trial from somewhere if you don't have one).
I also found this from a minecraft help page:
You cannot make a purchase from outside of the US using a credit or debit card issued in the US.
Due to US law, many or all prepaid debit cards (such as Visa Vanilla) purchased in the US will not work for purchases in our online store, as Mojang is located outside of the US.
Gift codes are not available for purchase in our online store from the US. Please consider buying a Minecraft prepaid card or a gift code on Amazon.com.
And
Try your purchase on another web browser or device, and make sure that the browser you are using is updated.
Consider trying a different payment method in our online store. There are several different payment methods available depending on the country. Click the displayed options or the link "More payment methods" as shown in the image below.
[media]If you are still not able to make a purchase, you may be able to buy a Minecraft prepaid card.
Here is the rest of that page: https://help.minecraft.net/hc/en-us/articles/360029642712-I-can-t-make-a-purchase
This doesn't look like a bug of any kind and I suspect you just have slow internet. Go to speedtest.net to see your speeds.
Can confirm in 1.16.5
I could not recreate this bug following your steps but I came across this in my own world and it affects an entire line of chunk borders (So a single line of chunk borders going from the west world border to the east). But the weird thing is that it only happens when my render distance is at 10 chunks. My ticket for extra information: MC-213646
@Anthony Cicinelli I did recreate this bug in a vanilla environment before submitting the bug and it persisted. Please tell me I don't have to submit a new bug report
This is not a bug. This is just how they decided to make the hitboxes
No I haven’t. I even thought about this myself and reset all my F1-F12 bindings (none of which were F3 or F4).
In the meantime, if you are using Google Chrome then you can use it's inbuilt feature that lets you translate pages automatically (It should be in the right side of the address bar or you can right click on the text and select "translate to [Language]" depending on what language you have set)