Blackmagic Camera App produces stuttering video

Hello there!

I am currently working on a school project for which I have downloaded the Blackmagic Camera App to utilize all the great features of the iPhone 15 Pro. I have connected an SSD (SanDisk Extreme 1TB, 1050 MB/s) to the phone via a standard USB C cable from Apple. I record in Apple Pro Res (so Apple Log and P3-D65 if I understood it correctly). The problem I have is that after 15 to 30 seconds the video starts to stutter and displays the same frame for a few seconds only for it to then jump a few seconds forward and display that frame for the next few seconds. I will attach the exported files (because I somehow can't attach mov files) in this thread so you can get a better understanding of what I mean. Again weirdly enough the stuttering only starts at about 15 to 30 seconds after the start of the recording.

If anyone has any ideas why this could happen, please let me know. I will update this thread if I have found another solution in the meantime.

Many thanks in advance!

Edit: I realised that the files are too large to attach here so I will create a WeTransfer link so you can download them there instead.
here is the link: https://we.tl/t-SDOsy0DJvE

I started experiencing this issue in the past week. I'm thinking it could have been introduced in the recent app updates. Really hope they fix it soon.

I record with the Black Magic Camera App on my iPhone 15 Pro Max in Apple Log H.265 (have done this for over 6 months). I've tried various frame rates and all seem to randomly stutter after recording for a minute or so.

I've been trying to record things this past week, but this issue has made the app unusable. I recorded some clips and then noticed the stutter so I rerecorded them but still encountered the stutter issue. And not to mention when I'm vlogging, I can't rerecord those things.

Original issue: After a minute or two of recording, the footage starts to stutter. Looks like it's flipping back and forth to previous frames. Audio sounds fine, but the video is unusable.

UPDATE: I deleted and reinstalled the app and haven't experienced the same stuttering yet. BUT I noticed that it starts to drop frames after about 20 min of recording...

Device and recording details:
Phone: iPhone 15 Pro Max
App Version: Blackmagic Cam 1.4.000041
Storage: Device storage in app
Codec: HEVC (H.265)
Resolution: 4K
Color Space: Apple Log - HDR
FPS: Various (all have issues)

I posted this on reddit as well to see if others had the same issue (I'm not allowed to post urls for some reason):
r/blackmagicdesign/blackmagic_cam_app_video_stuttering

viewtopic.php?f=18&t=202425

I'm running into some stuttering issues too and also found this post that sounded similar. I ran into mine at 8:30 and it seems to be a pretty regular pattern of frames in the wrong order

I've experienced a similar problem recording high frame rate video on my android phone (Galaxy S21 Ultra). The explanation might be similar though. I figured out that my phone was overheating from needing to process the HFR video and the processor speed was automatically throttling down, causing it to drop frames. The same may be happening with your iPhone when you're really maxing out the video capabilities while shooting longer clips. A thin phone with no internal fan and no way to dissipate heat is going to have limitations when you really push the processor. The same is true for DSLR's, which are notorious for overheating on longer shoots. Dedicated video cameras often have a fan so they can shoot continuously.