The sheet music doesn't play properly.

When I'm try to play sheet music, I find that buffering was severe from a few days ago.
Before than, MuseScore played the sheet music naturally.
But After I found this problem, every score I made has been buffered.
Though I deleted and re-install several times, installed vaccines on my Computer, and Downloaded and Changed soundfont, The problem has not been solved.
This problem is so severe that I can't play and check sheet music on Musescore.
The problem has been started after I tried to replace monitor.
I tried to the new monitor to the computer body, but the port doesn't fit.
So I'm using the existing monitor until port converter is purchased.
I feel strange that Musescore has been buffred after I tried to replace monitor.
If you can explain why, and know how to solve this problem, Please tell me as soon as possible.
I'm not good at English, so I want to reply in Korean Language if you possible.