Hello User 1826,
Welcome to the Microsoft community.
Normally only one on-screen keyboard can be turned on.
However, when we tested this, we found that if the on-screen keyboard was turned on before the PC went to sleep, two on-screen keyboards did appear after going to sleep and then turning the on-screen keyboard back on after going back to the desktop.
Although the steps to reproduce the problem may be different from what you did, we did reproduce your problem and the lag etc. that you described.
This appears to be a system issue, and we have sorted out the issue and provided feedback.
If it's convenient for you, you can also give feedback to Microsoft about your issue by following the steps in the website below, which will help the issue to be resolved as soon as possible.
Send feedback to Microsoft with the Feedback Hub app - Microsoft Support
If there's anything that's not clear, don't hesitate to let me know.
Sincerely
Carlos - MSFT | Microsoft Community Support Specialisto