Thanks for pointing this out... I am very sorry that this happened. I have not tested the .onion front-end much.
Sorry for missing this post, I was traveling during holidays last month.
The server that is serving the .onion front-end is running only that service, and so I doubt it is ever under heavy load. I am not sure if this was a problem with the onion network itself, with the front-end, or the instance. When I looked into options I could not find examples of Lemmy instances using .onion front-ends and I picked the one I did because it does not require JavaScript.
I will make an effort to use the .onion site myself more often and I will look for other options.