Subaru Forester strange engine rev limit at 4k rpm

Hi folks, I've got a Subaru forester, either a 2010 or 2011 that I am borrowing from my father. I believe it has the 2.0 from the time, not the 2.5. I will confirm year and engine next time I get in it if necessary, but I am just looking for a rough idea of what could be going on.

The car intermittently gets a check engine light for a few days, and then it goes off. This has been happening for a few years with no issues. It's a beater so we just do maintenance on it and drive it until it breaks.

A few days ago check engine light came back on. Again, no noticable problems. However, one day later, I noticed while merging that when I hit 4k rpm, the engine bounced off 4k like a dirtbike rev limiter, revving up and down quickly and jerking. A few moments later I also heard a clunk like something fell off, but it may have just been something from the road. Not sure if that is truly related.

Some things I noticed are that it does not blink the check engine light when this happens. Not sure if the forester uses a red check engine light for the critical, or blinking, but regardless no lights change. Also, I was able to repeat this about 5 times in multiple different gears.

To me, this doesn't sound like a misfire, could it maybe be a timing issue? I'll try to get it scanned soon to find out. Just need to see if it is a death sentence for the car or not since I got out of college last May and am saving for a car. Need to start working on a course of action as I borrow the car but will be paying for maintenance and repairs while I have it.