I am also seeing this with GoPro HERO8 Black.
While asking a different question, I realized that the main reason why my camera’s sequences look so “fisheyed” is because Mapillary seems to apply the wrong correction to this model. I have used various settings and they are all equally incorrect. I do not believe this has anything to do with camera’s firmware (as far as I now understand, Mapillary only uses the camera model to determine what correction is applied). Looking at recent uploads, other GoPro models like 7, 9, or 10 appear to have pincushion distortion applied (cancelling fisheye) while 8 has barrel distortion applied (making it even more fisheyed).
I believe the calibration data for this camera was added in this commit, specifically the camera_calibration.yaml for this model. This does match OP’s February photos being fine but later April’s photos not being fine. (But I might be wrong depending on what release was used, when they were actually uploaded, and when and how or if Mapillary applies correction retroactively.)
I will continue to tag my photos with the correct make and model EXIF tags and hopefully Mapillary can reprocess the images at a later date.