Playback lag after render

Hello,

Since the most recent Premier updates (12.1 & 12.1.1) I have been experiencing lagging during playback, but only after the clips have been rendered. While I am editing, un-rendered clips will playback fine. I generally have the playback resolution set to 1/2 with no lag and if the files are un-rendered I can set the playback resolution to full and will notice minimal lag during playback.

Once I render the files I cannot playback the video without lagging at any resolution setting. If I do lower the resolution to 1/4 the lag is less but is still severe enough that making additional edits is very difficult. The work around I've been dealing with is to delete the render files so that I can make additional edits and view the un-rendered files without lag.

I am working on a iMac (27-inch, Late 2012)

Processor 3.2 GHz Intel Core i5

16 GB 1067 MHz DDR3 Memory

NVIDIA GeForce GTX 675MX 1024 MB Graphics

I have the factory 1 TB HD with 711.99 GB of free storage.

Any help or direction of how to best resolve would be appreciated.