Performance decreasing whilst on server Mineplex

Hello there kind people!

Im having a issue on Minecraft Bedrock on the public server „Mineplex“! 
As mentioned above I am using a Nintendo Switch on Systemversion 9.1.0, with the latest 1.14.20 Hotfix. While I am playing on that server, the Performance/Framerate decreases a ton! 
only after 2 minutes ideling... the game becomes unplayable. (see video footage) Even if I leave the server, it stays like that even in the titlescreen. Any ideas?