Sample rate struggles

[lavastudios]

Hey gang,

I'm on PT 11.3.1, OS X 10.10.5 with a 15 inch Mid 2015 MacBook Pro and an SPL Crimson V1 interface.

A couple of times recently I've been sent sessions from other studios which I've opened only to find the playback is pitched too low. In both cases the original sessions were recorded at 48 kHz. I normally work at 44.1 and have no issues with sessions I've created, but nothing I do seems to fix the speed of these shared sessions. I've tried creating new sessions at 48 and importing the audio files (which I can see are 48 by right clicking them in Finder and looking at Get Info, and which Tools tells me "can be directly added to the current session"). But even when my Tools session appears to be at 48 (according to the Session window), the imported 48 kHz audio files also play back pitched low, as if my session was 44.1.

The first time this happened, I was in a rush and converted the 48 kHz files from 44.1 to 48, which was a band-aid fix for the issue. But it's happened again today with another 48 kHz session from a different studio, and I want to get to the bottom of it this time. Early on while troubleshooting, I wanted to rule out the files themselves being responsible, so I tried auditioning them from the Import --> Audio window. When I did, I got the following error:

A CPU overload occurred. If this happens often, try increasing the "H/W Buffer Size" in the Playback Engine Dialog, or removing some plug-ins. (AAE -6101)

I've since confirmed that the files play back at the correct speed when opened with other programs, but I get that same error message any time I try to audition those files from the Import --> Audio window in Tools. To confirm my hunch that Pro Tools was actually in 44.1 although it claimed to be in 48, I recorded a quick bit of audio of me speaking into the session. The file Pro Tools created is indeed a 48 kHz file, but when opening it in any other program, it plays pitched too high, as if it's a 44.1 file being played at 48. So then I tried changing the interface and using the MacBook built in output. The session now plays back in the correct speed with the exception of the small snippet of audio which I recorded as a test, which plays back pitched too high. So something about the way that Tools and my interface are communicating about clocking when the session is in48 kHz seems to be the issue. Does anyone have any thoughts on how I would go about fixing this?

Thanks in advance, and happy new year!