Question about Microsoft Sculpt Ergonomic

Hello together I am actually very happy with this keyboard/mouse that I bought in April 2020 and March 2022. Recently, I've been experiencing more and more problems with individual letters not working. That is, I press them and they are not written. It usually works after several attempts. Have any of you experienced this problem? I have already tried changing the batteries and plugging the dongle into a different USB port on the computer. Changing the batteries doesn't help, using a different USB port sometimes does. I use two different keyboards on the same two computers (home office and on-site) and the problem occurs periodically on both computers and both keyboards. It is therefore completely unclear to me what the problem could be... There is no driver that can be updated and I have not been able to find out if/how the firmware can be updated. The Microsoft Mouse and Keyboard Centre is installed, but I don't see anything that helps. Greetings, Richi