Hello, I have had my 2017 WRX Base for 2 years now, bought as 3rd owner, and over my two years I have put around 34k miles on it(Has been daily driven and road-tripped quite bit) and it currently sits at 103k miles. This will be a bit of a longer post as there has been a lot that has been involved in this issue.

I had no major issues besides replacing 2 wheel bearings and standard maintenance since owning. That is until this past August. I all of a sudden had a subtle misfire from cylinder 1 when between 10-12lbs of boost. The interval of the misfire was too short to generate a CEL or code. Could only get the misfire code to generate during a live data check while driving in that boost range.
I replaced spark plugs twice(first with platinum plugs, next with iridium), then replaced the cylinder 1 coil. Neither fixed the issue and rather temporarily made it better.

After battling it a couple weeks I finally took my car to Subaru, there the tech concluded it could be turbo related, as they stated in high(er) mileage shaft play is sometimes common. They were able to find inadequate shaft play in the turbo and there was a hole in the sump return hose. After replacing both the issue completely disappeared for a week, to which it returned but instead it would misfire/hesitate in any form of positive boost (0psi or higher), This occurred for 20 or so miles before the hesitating/misfiring began happening under any form of acceleration, also throwing a CEL. The car also began idling high and poorly sounding. The engine also began sounding very tractor like when accelerating.

I had my car towed to Subaru from the roadside and have been waiting to hear back. I already had a compression test/leak down scheduled for this week as I noticed the issue reappearing but didn't make it far enough obviously to get there. I was wondering if anyone has any thoughts on the issue or has had something similar occur to them before as I have been unable to find a forum of someone with a similar issue happen.

I'm not at all an expert, but I know when I had spun a bearing you could hear a knocking noise at idle and it would get louder if you raised the RPM at all. I had something somewhat similar with a bad MAF sensor. what is the CEL code?

This sounds like an air/spark/fuel issue and not like engine failure, and in that order. MAF, vacuum leak, bad coil(s) are where I'd start.

is your misfire always in the same cylinder? If so you can start by swapping that cylinder spark plug with another cylinder and see if it follows. After that, check for vacuum leaks between the maf and the manifold. if measured air is getting in or out somewhere, that could do it too. Misfire comes down to spark, fuel, or compression. Start with the easy ones first and keep your fingers crossed its not loss of compression.

Certainly, swap coils as suggested above to eliminate the coil or plug as the problem. At this mileage, check valve clearances. You may have a valve not seated correctly due to reduced clearance, and getting misfires due to reduced compression.

This happened to me, ended up burning a valve under light load, part throttle boost.