From your wording I see English is not your first language so I will try and explain this as clearly as I can. Vapour us only trying to help, but is frustrated at your wording and lack of details.
Your wording is wrong. A “Known Issue” with a game is an issue that has been well detailed, explained, and documented, including log files, and a clear written explanation of what has occurred. It is also an Issue that has been documented in a similar fashion by many other people, rather than just one. That makes it an issue that has happened to lots of people in different places with their own PC’s who all sent in their log files for LE to examine, so then a “known issue”.
An Issue that is felt by One person is “your issue”, and it is only from the information that YOU provide in the support forum or in a ticket that it can be theorised about as to its cause. Without details, no one has any idea what the actual problem is.
For example, you mention that you played on Ultra for 5 days, then after the patch you had 20fps. All we know from that is that you have fps drop. You have not provided any log files in the tech support forum that anyone can look at to try to help you.
Let me explain that in another way. You take your car into a mechanic. You say “I put Diesel in it, now it does not work properly,.” That does not help the mechanic have any idea what is really wrong, or how to help to fix it. If you had described to the mechanic what exactly was happening with your car that was different, he might be able to know the real problem and guess at the cause.
For your fps drop, no one can help you or even begin to “make a patch” until you provide more exact details. The best way you can do that is to send in your log files for someone to look at. We don’t know what PC specs you have, what OS you are using, whether it is the standalone or Steam client, or anything else. These are basics that people like Vapour, the other vets in here, or customer support will need to know. Your log files contain a whole bunch of data that can tell us what platform you are using. This is why often people send in a dxdiag log file as well as the game log files at C:\Users\yourname\AppData\LocalLow\Eleventh Hour Games\Last Epoch
Those files are le_graphicsmanager.ini, Player.log, & Version.txt
I hope this helps 