Never had this issue before. After upgrading from MC25 to MC26, i notice windows defender is creating issues. High CPU usage, stuttering video and unresponsive MC26. I followed the suggestions of turning off scanning and exempting MC26 files and directories, with no success.
I finally resorted to disabling real time protection.
MC26 is now back to normal, very snappy, CPU usage is sub 30% when viewing / recording etc. Previously it was up to 50%, with defender hovering at about 20% all the time.
I’m not sure what has changed between MC25 and MC26, but is a Microsoft or JRiver issue.
I hope there is a solution, as im running a system (be it only a media centre and not used for general access) without antivirus protection.