I been checking a few things on this saving a reply. I find replies here takes longer than the other communities and wonder if site specific ,or browser specific.
I have found that as you save it, there are times you will get the gateway or timeout error messages. So before you try to create a new message, you can close the error message and wait 15 seconds.
If the reply is still on the page, it will take about 15 seconds for it to post after the error message. If it not showing up, you should try to wait the 15 seconds and then refresh the page.
I know that Anker is taking about 5 to 6 to post a comment and Eufy community takes about 3 to 4 seconds with no issues posting. It seems like for me it takes way too long for it to save and usually get error messages.