GDimitrov,
1) What is your version ? It was fixed in the SubBuild 2019.11.19
2) First, update to the latest version if you don't have it.
Then could you check 2 things :
a) Check your GPU & CPU temperatures ; if one or both run too hot, turn on V-Sync in the Video options if you had turned it off
b) Launch the Windows' Task Manager, and check if TE4 is eating a big amount of RAM (ie: maybe I created some memory leak and once the game has eaten all the available memory, it gets very slow

)