I keep seeing "Sorry, a problem occurred while processing your request. Please try again later." too frequently these days (Germany). I mostly use GPT4o for its speed but that occurs with other models as well. This is especially painful when I use code assistant for debugging the problem and have accumulated some context. There is no option to restart the conversation and once I see this message, it basically means the end of discussion. However, if I reopen the chat and start the new discussion, it works. It feels like a machine which is serving the communication is taken out and the "refresh" fails to reconnect.
All in all, the stability of the chat assistants has deteriorated in the last few months and it definitely needs to improve or there should be options to save the context of the conversation to reintroduce it later when the communication is reestablished.