Cpu usage problem with 1 track

[why_vincent]

I don't know what has happened but suddenly I am getting CPU overload every 2-5 seconds when I am playing back audio. Keep getting -6101 error.

The system:

• Macbook 13 2013
• Interface: Tried both internal and apollo twin
• Pro tools 12.6
• Mac OS Sierra

The scenario:

• 1 audio track.
• 24 bit 44.1 kHz as project settings.
• No plugins.
• No Eucon.
• 1024 buffer size.
• 3 GB cache size.
• No external monitor.

All I did is try to record audio and try to play back audio(that I had to take from a different project since I cannot record). The projects I had open last week had 40+ tracks and many effects on with no problem.
It is impossible to work and I don't want to buy a new computer when the CPU usage is at 1-2 % just because of a bug in PT.

There is not even a CPU-spike in the activity monitor. Where do I go with this problem? If anyone can help me then I am eternally grateful.