From the description you are saying that the issue may be related because events are stucked into \Events folder. Do you see any improvement if you move events of \Events folder to outside ePO directory?
Which version of browser are you using?
Please reproduce the issue with different browser (like supported version of IE/Mozilla) and see if you see any difference.
I did try with different browser however the problem still persist. So, just now we already resolved and able to find the root caused of the event flooding inside Event folder. But main issues that I saw after upgrade to Patch 4 is tomcat5.exe uses very high CPU usage more that 50%. If I started the EventParser services, for sure epo will running so slow and will disconnect/ failed to login. My question is, why epo 4.5 patch 4 using high CPU usage compared to before?